Presence, Claim and Identity

2025-11-05T00:00:00+00:00

Presence, Claim and Identity #</a> </h1>
The purpose of this essay is to provide a standardized model for managing decentralized online identities. Specifically, it deals with how numerous online presences are associated and belong to the same identity, and provides a way for managing claims and identities of one's counterparts.</p>
Similar to Keyoxide</a>, it ensures one is interacting with whom they intended to be by helping check the authenticity of the counterpart's claims. Different from Keyoxide, it doesn't base an identity on any single profile (ASP, OpenPGP, etc.); claims can be made by any presence on any presence. Additionally, it doesn't deal with the technical aspects of formatting claims and verifying proofs.</p>

Table of Contents #</a> </h2>

Summary</a></li>
Presence</a></li>
Claim</a></li>
Identity</a></li>
Medium-specific Adoption Tips</a></li>
Implementations</a></li>
Glossary Translations</a></li>

Claim Boilerplate Translations</a></li> </ul>

Summary #</a> </h2>

The structure of a sample database adopting the proposed model is illustrated below.</p>

</p>

The model is based on three core elements: presence, claim and identity, hence the abbreviation PCI.</p>

An online account or a more fractional existence is recorded as a presence, represented by a smaller rectangle in the diagram above.</p>

When a presence claims to be in control of another presence, a claim is recorded in the diagram as a one-directional arrow pointing to the claimed presence.</p>

Presences that are inter-claimed are associated and belong to the same presence group, represented as a larger rectangle containing all these presences, the label of which being its identity. A presence being outside a group means it's not under common control with any presence in that group.</p>

Presence #</a> </h2>

A presence</strong> is a distinguishable existence on a medium of communication which can be interacted with. Examples of a presence are an OpenPGP key, an XMPP account (or an OMEMO device thereof), and a Matrix account.</p>

In practice, each presence is distinguished by a unique name. The general principle of naming a presence is to include the name of the medium plus the amount of information enough for distinguishing the presence from other presences on the medium. Example formats for naming presences on various mediums are listed below.</p>

Medium</th> Format</th> Example</th></tr></thead>

OpenPGP key</td> openpgp:<fingerprint></code></td> openpgp:123456789ABCDEF0123456789ABCDEF012345678</code></td></tr>

XMPP account</td> xmpp:<jid>[#<omemo_fingerprint>]</code></td> xmpp:alice@example.org</code>, xmpp:alice@example.org#123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0</code></td></tr>

Matrix account</td>

matrix:<matrix_id></code></td>

matrix:@alice:example.org</code></td></tr>
</tbody></table>
A presence may be revoked</strong>, if the medium of that presence supports declaring that the presence issuing revocation shall not be used any more. Revoked presences cease to exist and are removed from the database.</p>
Claim
 #</a>
</h2>
A presence may claim</strong> another presence. Through a claim, a presence unilaterally declares, in natural language, that the claimed presence is under common control with the presence making the claim.</p>
</p>
An example claim on an XMPP account written in English would be (available translations attached</a>):</p>
I hereby confirm that the following XMPP account:</span></span>
	alice@example.org</span></span>
and the OMEMO devices connected to it with the following fingerprints:</span></span>
	- 12345678 9ABCDEF0 12345678 9ABCDEF0 12345678 9ABCDEF0 12345678 9ABCDEF0</span></span>
	- 9ABCDEF0 12345678 9ABCDEF0 12345678 9ABCDEF0 12345678 9ABCDEF0 12345678</span></span>
are under my control.</span></span></code></pre>
A claim may be revoked through a similar declaration by the presence that made the claim, stating that the claimed presence is no longer under common control with the former presence. Revocation of a claim doesn't render a presence revoked; however, when a presence is revoked, all its claims are revoked as well.</p>
When two presences claim each other, they are associated</strong>, meaning it's confirmed that both presences are under common control. When so, they belong to the same presence group</strong>.</p>
</p>
Specifically, a single presence not associated with any other presence also forms a group.</p>
An association between two presences from different presence groups combines</strong> the two groups into one.</p>
</p>
Absence of an association (due to revocation of a claim) in a presence group may or may not dissolve</strong> the group into more than one independent groups, depending on how presences are associated within.</p>
Identity
 #</a>
</h2>
A presence group is by default unidentified. To identify</strong> a presence group is to recognize the control of the group as a definite entity by giving it a unique name. In other words, to identify a presence group is to name it.</p>
Identity is group-level. Therefore, identifying any presence in a presence group equals identifying that group; it makes all other presences in that group identified the same.</p>
When an unidentified presence group combines with an identified group, the identified one infects</strong> the unidentified one with its identity. From another perspective, the unidentified group contracts</strong> the identity from the identified one.</p>
</p>
When an identified presence group is dissolved into more than one groups, all resulting groups turn unidentified, since identity is unique and no more than one groups may be identified the same. Note that a single presence leaving an identified presence group also constitutes dissolution.</p>
</p>
Presence groups dissolved into may be identified again. In this scenario, one may want to identify one of the resulting groups as its previous identity, or not identify any of them any more.</p>
Due to various reasons, one physical individual may have multiple identities. In this case, their identities should be treated as separate ones, and no association should be assumed between any of their presences.</p>
Medium-specific Adoption Tips
 #</a>
</h2>
XMPP
 #</a>
</h3>
In Gajim, consecutive messages from the same JID are merged into one block, even if they are from different OMEMO devices. To be able to see the OMEMO fingerprint of each message, go to Preferences → Advanced → Advanced Configuration Editor, and deactivate chat_merge_consecutive_nickname</code>.</p>
Implementations
 #</a>
</h2>
An example CLI program sam</code> is created that adopts this model for managing decentralized online identities. The program is released here</a>.</p>
Glossary Translations
 #</a>
</h2>
English</th> Mandarin</th></tr></thead>

presence</td> 现身</td></tr>
to revoke</td> 吊销</td></tr>
claim</td> 声明</td></tr>
to claim</td> 声明所有权</td></tr>
association</td> 关联</td></tr>
to associate</td> 关联</td></tr>
presence group</td> 现身组</td></tr>
to combine</td> 合并</td></tr>
to dissolve</td> 解体</td></tr>
identity</td> 身份</td></tr>
to identify</td> 标识</td></tr>
to infect</td> 传染</td></tr>
to contract</td> 感染</td></tr>
</tbody></table>
Claim Boilerplate Translations
 #</a>
</h2>
Translations on the example claim on an XMPP account written in English</a>.</p>
Mandarin
 #</a>
</h3>
本人特此证实，如下 XMPP 账号：</span></span>
	alice@example.org</span></span>
及属于该账号且指纹如下的 OMEMO 设备：</span></span>
	- 12345678 9ABCDEF0 12345678 9ABCDEF0 12345678 9ABCDEF0 12345678 9ABCDEF0</span></span>
	- 9ABCDEF0 12345678 9ABCDEF0 12345678 9ABCDEF0 12345678 9ABCDEF0 12345678</span></span>
均受本人控制。</span></span></code></pre>

This page is released into the public domain under CC0 1.0</a>.</p>


Two Weeks of Learning Toki Pona
2025-07-22T00:00:00+00:00
Two Weeks of Learning Toki Pona
 #</a>
</h1>
You may or may not have heard of Toki Pona</a>. If not, in a word, it is a popular conlang (meaning a human-made language) second only to Esperanto, with only 100+ basic words and simple grammar. Despite the simplicity, it is, as it claims, already a complete language capable of handling any topics with clarity and comfort.</p>
I had already known of the language for quite a while but had never learned it until two weeks ago. Then, having been in a MUC of friends for some time where everyone else except me speaks Toki Pona, I decided to actually learn the language.</p>
In two weeks, or more precisely 12 days, I finished my Toki Pona course, which included learning all the grammar and memorizing all the core and common words, with what's left to do being further honing my language skills through massive inputs and outputs because obviously you can't actually master a language in just 12 days. The experience, though, was fun and pleasant throughout, and I would certainly recommend that you have a try at it as well.</p>
Learning resources
 #</a>
</h2>
To begin with, I chose the course lipu sona pona</a>, which literally means "the good book." This is an online course well divided into 12-13 lessons, each a day, and is what my learning is mainly about. I also used Wasona</a> as an auxiliary resource, as it provides some useful Q&As and complementary information.</p>
While kick-starting your learning, you probably want to watch this video</a> to get a general idea of how Toki Pona works. This way, most grammatical points will feel more familiar to you in later lessons. This cheat sheet</a> could also be a useful quick reference.</p>
For the vocabulary part, instead of just relying on the short English translations provided by the course for word definitions, I would recommend using an online Toki Pona dictionary like lipu Linku</a> or nimi.li</a>. The two are based on the same dataset, but I personally prefer using the latter because of the interface. What's important is that, apart from just providing a few English translations, they also provide other helpful information such as word usage, origin and most importantly, semantic space. With each entry, there is an article about the semantic space of the word that describes in greater detail what the word is and is not about, which I find very helpful in understanding a word.</p>
The experience
 #</a>
</h2>
With all the resources, how has my learning gone? It actually went smoothly. Learning the language wasn't a difficult experience, and all it took was time.</p>
The easiest part is grammar. Thanks to the aforementioned video and  sheet, I was already able to have a good grasp of the grammar in the very first days. Toki Pona was designed to be easily learned, so the grammar was simplified to the maximum extent possible - no tense, voice, person, number, gender, inflection, or anything else. The grammar, though sometimes causing a little bit of ambiguity, is a lot simpler than those of Chinese and English, the languages which I speak, where there are random exceptions everywhere.</p>
Being able to speak both languages also helped me learn the vocabulary. All words in Toki Pona originated from existing languages in the world, and there are quite a number of them from Mandarin, English, and their sister languages. But I bet not considering their origins, you'll still have a pleasant time memorizing them, as the spelling and pronunciation are so simple, and you don't have silent letters or suspicious syllables like those you get in English, plus there are only 120-140 words to remember after all. By the end of day 10, I had already memorized all core and common words - no flash card apps used and no rote memorizing. The key is to consult the dictionary often and familiarize yourself with the words through various inputs.</p>
By various inputs, of course, we are not just talking about the course materials. There is this Toki Pona library</a> that contains various works written in Toki Pona, though I personally haven't used it. However, while learning the language, I do come across some awesome Toki Pona songs like telo sewi</a>, ale li ante</a>, mi jaki</a> and Toki Pona Caramelldansen</a>. Some of them are extremely cute, and some of them are extremely emotive, but overall it's fascinating seeing how much such a simple language can express.</p>
Listening and speaking (aloud) is definitely an important part, because learning a language is not just learning to read and write it. During the past two weeks, I repeatedly listened to those songs and gradually found myself understanding more and more of the lyrics. I also tried to transcribe the song and translate it and compared my work with the official lyrics to see where I went wrong. A general tip for listening is to not listen syllable by syllable or word by word, otherwise you'll have a hard time understanding something like "soweli lili li..." Instead, group the speech in chunks, and try to recognize and remember some common collocations of words and sentence patterns. The same applies to speaking.</p>
Conclusion
 #</a>
</h2>
Again, the two-week experience was pleasant and fruitful. It was also an experience about learning to simplify my thoughts and express everything in 130-ish words.</p>
While two weeks is, I think, the average time it takes to finish the basic courses, it certainly takes many months or years to get really fluent, as I've seen from many fluent speakers in the community. Thus, I'll probably continue honing my Toki Pona skills and see how far I can eventually get.</p>

This page is released into the public domain under CC0 1.0</a>.</p>


Sound System Setup for Acoustic Guitar Recording and Streaming
2025-04-05T00:00:00+00:00
Sound System Setup for Acoustic Guitar Recording and Streaming
 #</a>
</h1>
This is my rather unprofessional sound system setup for internally recording and streaming guitar performances on my computer.</p>
In summary, it consists of an amplifier that picks up sounds through a guitar pickup and then transmits them to my laptop through a 3.5mm cable. Recording and streaming are mainly to the credit of OBS and a PulseAudio setup.</p>
Guitar pickup
 #</a>
</h2>
Turn the humbucker pickup volume as high as possible without distortion. To see if there's distortion, listen to the sounds from the amp rather than the computer.</p>
If available, turn up the internal microphone to a relative high level to be able to pick up percussive sounds.</p>
Amplifier
 #</a>
</h2>
Turn input volume to maximum (100%), but do not tweak the bass or treble knobs.</p>
Disable the loudspeaker, then turn the output volume to maximum (100%) to ensure highest S/N ratio in the analog transmission.</p>
Cabling is a bit tricky. Thanks to my ThinkPad having only a combo jack, I had to use a 4-pole audio cable.</p>
Recording
 #</a>
</h2>
In OBS sources, create an Audio Input Capture (PulseAudio)</code> and choose the input device. Do not rely on global audio devices (the ones in the Audio Mixer by default), since they follow the system default, which may automatically change when unplugging the cable. Global audio devices can be disabled in the settings.</p>
In the Audio Mixer, always keep the PulseAudio capture at 100% volume. When there's a need to otherwise turn input volume up or down, use pavucontrol</code> instead. Doing that in system settings is also okay, but is not as straightforward compared to the dedicated PulseAudio volume controller.</p>
Despite recording internally, there may still be much noise due to analog input. To tackle this, add Noise Suppression</code> to audio filters, preferably with Speex</code> method, which works best for me. Additionally, unplugging my laptop from power seems to magically reduce noise sometimes.</p>
Streaming
 #</a>
</h2>
Regular streaming with OBS should be as simple as recording. However, in conferencing software such as Jitsi, where direct access to microphone is the only option, the following PulseAudio tricks</a> need to be applied.</p>
First, create a virtual microphone named VirtualMic</code> which pipes audio from the virtual output device SinkForVirtualMic</code>:</p>
pactl</span> load-module</span> module-null-sink</span> sink_name=Source</span> sink_properties=device.description=</span>"</span>SinkForVirtualMic</span>"</span></span>
pactl</span> load-module</span> module-virtual-source</span> source_name=VirtualMic</span> master=Source.monitor</span></span></code></pre>
Then, go to OBS settings > Audio > Advanced, and select SinkForVirtualMic</code> for Monitoring Device.</p>
Finally, open Advanced Audio Properties, locate the actual input device, and switch its Audio Monitoring to Monitor and Output</code>.</p>
Now, VirtualMic</code> can be used as the input device for the conferencing software. To get optimal volume, also make sure volumes for VirtualMic</code> and SinkForVirtualMic</code> are set to 100% in Pavucontrol.</p>

This page is released into the public domain under CC0 1.0</a>.</p>


Issues with the English Version of the Mulan Public License
2024-08-25T00:00:00+00:00
Issues with the English Version of the Mulan Public License
 #</a>
</h1>
The Mulan Public License, Version 2</a> is a bilingual</em> copyleft license published by COSOL. It is approved by neither FSF nor OSI, though its sibling license, the Mulan Permissive Software License, Version 2</a> was approved by OSI as an "open source" license</a>. What I'm talking about today is, however, not license proliferation</a> or anything like that, but rather how problematic the English version of that license can be.</p>
According to its license terms, the Mulan Public License "is written in both Chinese and English", both "having the same legal effect", and "in case of divergence, the Chinese version shall prevail." I'm glad the English version doesn't look like it's machine-translated, but from what you're about to read soon, that could be exactly what extinguished my gladness.</p>
Starting from Section 0 of the license, we've already got a typo here:</p>

Affiliates</strong> mmeans</u> entities that control, are controlled by, or are under common control...</p>
</blockquote>
Moving on to Section 2, which is about grant of patent license:</p>

... such patent license is only limited to the patent claims owned or controlled by such Contributor now or in future ..., excluding of</u> any patent claims solely be</u> infringed by your modification.</p>
</blockquote>
There's no "excluding of", just "excluding" (the incorrect one is used in Section 0 as well). Also, just so it's grammatical, use "to be" instead of "be".</p>
For Section 4, we've got a lot to talk about:</p>

If you Distribute your Derivative Work, you have to</u>:</p>
(i) accompanying the Derivative work</u>, provide recipients with Corresponding Source Code</u> of your Derivative Work under this License...</p>
</blockquote>
In order to indicate requirements, "must" should be used instead of "have to". Also, "Derivative work</em>" is not capitalized, and a "the" is missing before "Corresponding Source Code".</p>

If you provide the Corresponding Source Code through a download link, you should place such link address prominently in the Derivative Work or its accompanying documents, and be valid no less than three years</u> from your Distribution of the particular Derivative Work, and...</p>
</blockquote>
The whole parallel construction grammatically indicates that it is you</em> rather than the link that should "be valid". To keep the subject consistent while expressing the correct object, use a causative verb. Also, a preposition is needed there for "no less than three years" to follow. Taken together, this becomes "keep it valid for no less than three years."</p>

(ii) accompanying the Derivative Work, provide recipients with a written offer indicating your willingness to provide the Corresponding Source Code of the Derivative Work licensed</u> under this License.</p>
</blockquote>
I venture that the word "licensed" is redundant, though the Chinese version does</em> make this part attributive rather than adverbial.</p>

Such written offer shall be placed prominently in the Derivative Work or its accompanying documents. Without reasonable excuse</u>, the recipient shall be able to acquire the Corresponding Source code</u> of the Derivative work for</u> no more than three months from your receipt of a valid request, and be valid</u> no less than three years from your Distribution of the particular Derivative Work.</p>
</blockquote>
Apart from "Corresponding Source code</em>" not fully capitalized, we're again faced with confusing subjects. Since the one keeping the written offer valid is different from the subject (the recipient) here, making the verbs parallel doesn't work anyway -- use a clause or a sentence instead ("you must keep it valid for...").</p>
For the adverbial part ("without reasonable excuse"), even if you believe in dangling participles (which are very dangerous in formal writing, not to mention this is not even a participle), saying "unless with" rather than "without" should make more sense. But since the subjects are indeed different, and there's no even a thing called "dangling preposition", use a clause ("Unless you have a reasonable excuse").</p>
I'll finally argue that the preposition "for" should be replaced with "within", the "from" after that thus replaced with "of".</p>
For the rest of the license, Sections 5 to 8 plus the Appendix, each of them got us something to talk about. And for the sake of readability, Sections 7 and 8 have been transformed to lowercase.</p>

[Your license will not be terminated, provided that] it’s your first time to receive</u> a notice of termination from such Contributor pursuant to this License, and you have cured all the breaches within 30 days of receipt</u> of such notice.</p>
</blockquote>
"Receiving" instead of "to receive". Also, add a "your" before that "receipt".</p>

If you combine Contribution or your Derivative Work with a work licensed under the GNU AFFERO GENERAL PUBLIC LICENSE Version 3 (hereinafter referred to as “AGPLv3”) or its subsequent versions, and according to the AGPLv3 or its subsequent versions, you have an obligation to make the combined work to be licensed under the corresponding license</u>, you can license such combined work under the license</u>...</p>
</blockquote>
"Corresponding license" is not defined, and if you take it literally, it may also be interpreted as something else other than the AGPLv3 or its subsequent versions. The same applies to the phrase "the license" that follows. In the Chinese version, however, "AGPLv3 or its subsequent versions" is explicitly used here.</p>

Contribution are</u> provided without warranties of any kind, either express or implied. In no event shall any Contributor or copyright holder be liable to you for any damages, including, but not limited to any direct, or</u> indirect, special or consequential damages arising from your use or inability to use the Contribution...</p>
</blockquote>
"Contribution" is not plural, as indicated elsewhere in the license as well. Also, "or" is redundant.</p>

In the case of</u> divergence between the Chinese and English versions, the Chinese version shall prevail.</p>
</blockquote>
"In case of", not "in the case of", since this is not about a specific case.</p>

Create a file named “LICENSE” which contains the whole context</u> of this License in the first directory of your software package;</p>
</blockquote>
I doubt if what they mean is "content", but "a copy of this License" just sounds much better.</p>
Conclusion
 #</a>
</h2>
While I've certainly got a lot more to talk about, I'm already tired of writing at this point. The steward could have been more professional.</p>

This page is released into the public domain under CC0 1.0</a>.</p>


混合作品的版权归属与许可证兼容性
2023-09-27T00:00:00+00:00
混合作品的版权归属与许可证兼容性
 #</a>
</h1>

本系列作品：</p>

版权法入门</a></li>
软件许可证入门</a></li>
混合作品的版权归属与许可证兼容性</li>
</ul>
</blockquote>
请不要被这个标题吓到！我们会使用尽量简单的语言，解释一些在协作软件项目时，常常会遇到的版权与许可证问题。本文使用了问答的形式来组织，这样你就可以只阅读你需要了解的部分。</p>


我能将软件 A 的源代码并入软件 B 吗？</a></li>
软件 A 的许可证不兼容软件 B 的许可证，就代表着 A 的源代码不能并入 B 的源代码吗？</a></li>
将软件 A 的源代码并入软件 B 时，我需要做什么？</a></li>
我可以更换软件许可证吗？</a></li>
我可以升级到新版本的许可证吗？</a></li>
有些项目要求我在对其贡献之前签署一份 CLA。那是什么？</a></li>
我可以收回我的许可吗？</a></li>
我可以修改一份许可证，或编写一份新的许可证吗？</a></li>
我可以为一份许可证添加附加许可吗？</a></li>
我可以为一份许可证添加附加限制吗？</a></li>
我可以为我的软件使用多份许可证吗？</a></li>
我可以让他人付费来豁免某个许可证的要求吗？</a></li>
各种许可证相互兼容情况如何？</a></li>
后记</a></li>
</ul>

我能将软件 A 的源代码并入软件 B 吗？</a>
 #</a>
</h2>
这主要取决于 A 的许可证是否兼容 B 的许可证。一般来说，自由软件许可证的兼容性有如下的关系：</p>

宽松型许可证 ⇒ 中间型（弱 copyleft）许可证 ⇒ copyleft 许可证</p>
</blockquote>
这里的箭头（⇒），代表前者的代码可以并入后者的代码，但反过来不成立。如果你还不理解这些类别的涵义，请阅读软件许可证入门</a>。</p>
例如，LGPLv3 是一份中间型许可证；GPLv3 是一份 copyleft 许可证。所以，你可以把 LGPLv3 下的代码并入 GPLv3 下的代码之中。同理，宽松型许可证下的代码，也可以并入中间型许可证或 copyleft 许可证下的代码。例如，MIT 许可证或 Apache 许可证 2.0 下的代码，可以并入 LGPLv3 或 MPL 2.0 下的代码，也可以并入 GPLv3 或 AGPLv3 下的代码。</p>
但是请注意，这只是通常的情况。有时候，一些许可证的老版本会导致不兼容。常见的例子如：</p>

Apache 许可证 2.0 不兼容 GPLv2，但兼容 GPLv3；</li>
MPL 1.1 不兼容 GPL，但 MPL 2.0 兼容它（但有一个例外，见下）。</li>
</ul>
还有一些其他的原因也会导致不兼容。例如，MPL 2.0 允许分发者附加一份声明，以禁止将该许可证下的软件并入 GNU 许可证，这样的话它就与 GPL 不兼容。详见完整的许可证兼容性表格</a>。</p>
软件 A 的许可证不兼容软件 B 的许可证，就代表着 A 的源代码不能并入 B 的源代码吗？</a>
 #</a>
</h2>
不一定。这只代表着在 B 的许可证不变的情况下，A 的源代码不能并入 B 的源代码。更换 B 的许可证之后，你就可能可以将 A 的源代码并入 B 的源代码。详见完整的许可证兼容性表格</a>以及如何更换软件许可证</a>。</p>
将软件 A 的源代码并入软件 B 时，我需要做什么？</a>
 #</a>
</h2>
这取决于软件 A 的许可证。</p>
如果软件 A 的许可证是宽松型许可证</strong>，那么一般要满足的条件是在软件 B 中保留软件 A 的署名信息。例如：</p>

当软件 A 使用 MIT 许可证或 BSD（2-Clause 或 3-Clause）许可证时，只需要在软件 B 的适当位置保留软件 A 的版权声明和许可证声明。</li>
当软件 A 使用 Apache 许可证 2.0 时，则对软件 B 有以下的要求：（1）附带一份许可证的副本；（2）标注修改过的文件；（3）保留源代码中的版权、专利、商标、署名信息等声明；（4）在适当位置保留随软件分发的 NOTICE 文件中的归属声明（如果有）。</li>
</ul>
如果软件 A 的许可证是 copyleft 许可证</strong>，则：</p>

以 GPL 为例，主要需满足的要求如下：（1）附带一份许可证的副本；（2）标注作品经过修改，并给出修改日期；（3）保留版权声明、免责声明等法律声明；（4）以同样的许可证提供软件 B 的源代码。</li>
对 AGPL 而言，则是在 GPL 的基础上，向通过网络服务使用软件 B 的用户，也提供该软件的源代码。</li>
</ul>
如果软件 A 的许可证是中间型许可证（即弱 copyleft 许可证）</strong>，典型的是 MPL 和 LGPL，那么 B 的分发条款可以自己任意选择。话虽如此，在分发作品 B 时也至少需要在 B 中满足这些条件：</p>

A 的许可证常见以下要求：（1）声明组合作品使用了软件 A；（2）保留 A 的版权和许可证声明；（3）提供 A 的许可证副本获取方法；（4）以同样的许可证提供 A 或其修改版的源代码。</li>
此外，LGPL 还要求你允许接收者使用 A 的修改版来组合一份 B 的重组版本。</li>
</ul>
以上是我们对一些常见许可证的义务进行的简单概括。如果你想要准确地了解某个许可证的具体内容，请阅读许可证原文。这里</a>有一些资源，是一些自由软件许可证的（非官方）中文翻译。</p>
我可以更换软件许可证吗？</a>
 #</a>
</h2>
可以。我们将这种行为称为再许可（relicensing）。</p>
如果该软件完全由你编写，没有来自其他人的代码，那么你可以直接对软件进行再许可。</p>
如果你的软件包含了并非由你写的代码，那么要进行再许可，则必须满足：</p>

这部分代码所使用的许可证兼容</a>你想要将你的软件更换至的许可证；或</li>
如果这部分代码的作者在向你贡献这部分代码时，已经提前签署了一份 CLA 或类似的协议</a>，其中明确同意将再许可的权利授予给你，那么你可以直接这么做。</li>
</ol>
如果以上都不是你的情况，那么你必须向这部分代码的原作者索取授权，才能进行再许可。</p>
请注意，如果你对软件进行再许可，新的许可证只会应用于软件的后续版本。在旧的许可证下发布的软件版本，其旧许可仍然有效。</p>
我可以升级到新版本的许可证吗？</a>
 #</a>
</h2>
同一许可证的两个不同版本实际上是两份不同的许可证，所以升级到新版本的许可证也相当于更换一份许可证，这是需要有权才能做的。请参看上一个问题</a>，了解能这么做的前提。</p>
然而，这里有两个特例：</p>

对于 GNU 家族的许可证（GPL、AGPL、LGPL）而言，

如果你在发布项目时，声明的是该项目是“以某许可证或其任何后续版本许可”，例如“以 GPLv2 或其任何后续版本许可”或“以 AGPLv3 或其任何后续版本许可”，则接收者可以在该版本的许可证，或其更新的版本下接收许可。</li>
如果你在发布项目时，声明该项目指定了一个代理方，代为决定采用哪个后续版本的许可证，则接收者可以在当前的许可证版本或代理方公开接受的后续版本下接受许可。这里</a>有一个项目指定代理人的例子。</li>
</ol>
</li>
对于 MPL 而言，如果你使用了 MPL 2.0（也就是目前最常用的版本）发布一个项目，那么接收者就可以在 MPL 的 2.0 版本或任何后续版本下使用该项目，无论你最初是否有允许在后续版本的 MPL 下使用该项目。也就是说，这个自动升级的机制是嵌在许可证中的，无需手动升级许可证，也不能避免这个机制。</li>
</ul>
有些项目要求我在对其贡献之前签署一份 CLA。那是什么？</a>
 #</a>
</h2>
CLA 即贡献者许可协议（Contributor License of Agreement）。部分项目要求贡献者签署一份 CLA 或者类似的文档，才能接受贡献者提交的贡献。</p>
这类文档的的内容可能因项目的不同而不同。有些只是为了确保贡献者是这些贡献的原作者，或有权提交这些贡献（例如内核 Linux 的 DCO）。然而，有些却要求你授予再许可的权利，甚至转移版权给他们。这样的话，他们后续就有权不经过你的许可而更换你的贡献的许可证，甚至是将它并入专有软件。</p>
如果你要贡献的项目要求你签署这类文档，那么一定要读一读它的内容。如果你认为它是不可接受的，那么你可以创建你自己的分支，而不必遵守该项目的 CLA 或类似文档，只需遵守其许可证。</p>
我可以收回我的许可吗？</a>
 #</a>
</h2>
不能。自由软件的许可是不能撤销的。只要用户接收到了你分发的软件，那么他们就永久获得了在其许可证下使用该软件的权利，即使你停止分发该软件或删除该软件的公共仓库。</p>
我可以修改一份许可证，或编写一份新的许可证吗？</a>
 #</a>
</h2>
修改一份许可证实则就是在编写一份新的许可证。我们强烈不建议这么做。如果你的目的是附加更多许可，那么请阅读这个问题</a>；如果你的目的是附加更多限制，那么请阅读这个问题</a>。如果你执意要编写一份新的许可证，那么要注意以下问题：</p>
首先，编写一份新的许可证需要考虑诸多法律问题，如法律效力和许可证兼容性。法律问题可能会影响其他项目对该项目的复用欲望。</p>
其次，你不能将你的许可证命名为诸如“GNU 禁止商业用途许可证”、“Apache 禁止修改许可证”或“Mozilla 仅个人使用许可证”。GNU、Apache 和 Mozilla 等名字是有商标的。如果你这么做，会造成商标侵权。</p>
再者，如果你要在你编写的新许可证中，改编来自其他许可证的文本，那么你可能还要获得这些许可证文本的版权许可。就我们所知，GNU</a>、Mozilla</a> 和 Apache</a> 允许了其许可证文本的再使用，但如前所述，禁止了其商标的使用。此外，GNU 还禁止其序言和附录的再使用。</p>
最后，如果要为一个已经在其他许可证下发布的软件，编写一份新的许可证，则需要确保是否有权对其进行再许可。请参看这个问题</a>，了解能这么做的前提。</p>
我可以为一份许可证添加附加许可吗？</a>
 #</a>
</h2>
可以。如果你希望某个许可证的限制条件不要生效或不要在某种情况下生效，那么你可以随软件的许可证声明再附带一段法律声明，说明你对这个许可证附加了怎样的例外情况。</p>
附加许可通常发生在软件使用了 copyleft 许可证的情况，用来在豁免某些情况下 copyleft 的适用性。例如在这种情况</a>、这种情况</a>或（稍微复杂的）这种情况</a>。</p>
为许可证添加附加许可，也就是把软件的许可证条款变得宽松了一些；这就类似于更换许可证，也是需要有权才能做的。请参看这个问题</a>，了解能这么做的前提。</p>
我可以为一份许可证添加附加限制吗？</a>
 #</a>
</h2>
通常不能以你预期的方式。</p>
许可证是有完整性（integrity）的。一般地，如果你对某个许可证添加了附加限制，那么你就不能再说你的软件“以 [原许可证的名字] 授权”了。</p>
有时，说某软件“以 [原许可证的名字] 授权，并带有某些限制”也是不可行的。例如，如果你使用 (A)GPLv3 发布某软件，并声称禁止用于商业用途，那么 (A)GPLv3 的第 7 节就会直接使这条限制失效。</p>
有些许可证确实允许存在一定的附加条款，但能添加的条款十分有限，并不能达到你想要的任意的限制条款。例如：</p>

MPL 2.0 允许作者禁止将软件并入 GNU 许可证下的软件中。</li>
(A)GPL 允许软件附带一些条款来保护名誉权或添加附加的免责声明。实际上，(A)GPL 许可证允许这些限制，只是为了让一些现有的许可证与之相兼容。</li>
</ul>
综上，为一份已有的许可证添加自己想要的任意限制，基本是不可行的。你需要编写一份新的许可证</a>。</p>
我可以为我的软件使用多份许可证吗？</a>
 #</a>
</h2>
可以。我们将这种行为称为双重许可（dual licensing）。</p>
你可以在软件的许可证声明中，声明“该软件以 [许可证 A] 或 [许可证 B] 许可”，这样的话，接收者就可以要么在许可证 A 的条款下接收该软件，要么在许可证 B 的条款下接收该软件。</p>
一些开发者有时会选择使用条款类似的多份许可证，来对软件进行双重许可。这么做通常是因为有些许可证条款类似，但兼容的许可证不同，而通过双重许可，可以扩大软件的许可证兼容范围。不过，这种行为已经很少见了。</p>
我可以让他人付费来豁免某个许可证的要求吗？</a>
 #</a>
</h2>
可以。我们将这种行为称为出售例外（selling exceptions）。</p>
出售例外与附加许可</a>类似，只不过他方是付费购买了这样的许可。以及，这种许可一般是授予至独家，而不是授予至公众的。</p>
这种许可模式并不少见。例如 Qt 框架是使用 GPL 许可的，这使得使用了 Qt 的程序必须同样使用 GPL 发布为自由软件。但开发者可以购买一份例外，从而有权将自己使用了 Qt 的程序发布为专有软件。</p>
各种许可证相互兼容情况如何？</a>
 #</a>
</h2>
针对一份 GNU 许可证与另一份 GNU 许可证的之间的兼容性，请参看 GNU 许可证兼容性表格</a>。</p>
针对涉及非 GNU 许可证的兼容性，请参看以下我们总结的表格：</p>

非 GNU</strong> 许可证与非 GNU</strong> 许可证的兼容性</a>；</li>
GNU</strong> 许可证与非 GNU</strong> 许可证的兼容性</a>；</li>
非 GNU</strong> 许可证与 GNU</strong> 许可证的兼容性</a>。</li>
</ol>
阅读下面的表格前，请先注意：</p>

“BSD”包括了 BSD 2-Clause 和 BSD 3-Clause 许可证。</li>
“MPL 2.0 NCE”是我们临时创建的一个代号，它表示“以 MPL 2.0 许可，不兼容次级许可”。根据 MPL 2.0，如果软件分发者在其许可证声明中，附加了一份 MPL 2.0 附录 B 中的内容，那么该软件就不能和一些许可证相组合。</li>
“某许可证+”表示分发者声明了接收者可以“在某许可证或其任何后续版本下”接受许可。</li>
当我们说“可以：组合遵循某许可证”时，则表示当前项目必须要更换</a>成那份许可证，组合才能进行。当我们只说了“可以”时，那么则无需更换许可证。</li>
</ol>
1. 非 GNU 许可证与非 GNU 许可证的兼容性</a>
 #</a>
</h3>
纵列表示要并入的代码使用的许可证，横列表示当前项目的软件许可证。</p>
↱</th> MIT / BSD 许可证</th> Apache 许可证 2.0</th> MPL 2.0</th> MPL 2.0 NCE</th></tr></thead>

MIT / BSD 许可证</td> 可以</td> 可以</td> 可以</td> 可以</td></tr>
Apache 许可证 2.0</td> 可以：组合遵循 Apache 许可证 2.0</td> 可以</td> 可以</td> 可以</td></tr>
MPL 2.0</td> 可以：组合遵循 MPL 2.0</td> 可以：组合遵循 MPL 2.0</td> 可以</td> 待研究</td></tr>
MPL 2.0 NCE</td> 可以：组合遵循 MPL 2.0 NCE</td> 可以：组合遵循 MPL 2.0 NCE</td> 待研究</td> 可以：组合遵循 MPL 2.0 NCE</td></tr>
</tbody></table>
2. GNU 许可证与非 GNU 许可证的兼容性</a>
 #</a>
</h3>
纵列表示要并入的代码使用的许可证，横列表示当前项目的软件许可证。</p>
↱</th> MIT / BSD 许可证</th> Apache 许可证 2.0</th> MPL 2.0</th> MPL 2.0 NCE</th></tr></thead>

LGPLv2.1</td> 可以：组合遵循 LGPLv2.1</td> 不行</td> 可以：组合遵循 LGPLv2.1</td> 不行</td></tr>
LGPLv2.1+</td> 可以：组合遵循 LGPLv2.1 或 LGPLv3</td> 可以：组合遵循 LGPLv3</td> 可以：组合遵循 LGPLv2.1+</td> 不行</td></tr>
LGPLv3</td> 可以：组合遵循 LGPLv3</td> 可以：组合遵循 LGPLv3</td> 可以：组合遵循 LGPLv3</td> 不行</td></tr>
LGPLv3+</td> 可以：组合遵循 LGPLv3</td> 可以：组合遵循 LGPLv3</td> 可以：组合遵循 LGPLv3+</td> 不行</td></tr>
GPLv2</td> 可以：组合遵循 GPLv2</td> 不行</td> 可以：组合遵循 GPLv2</td> 不行</td></tr>
GPLv2+</td> 可以：组合遵循 GPLv2 或 GPLv3</td> 可以：组合遵循 GPLv3</td> 可以：组合遵循 GPLv2+</td> 不行</td></tr>
GPLv3</td> 可以：组合遵循 GPLv3</td> 可以：组合遵循 GPLv3</td> 可以：组合遵循 GPLv3</td> 不行</td></tr>
GPLv3+</td> 可以：组合遵循 GPLv3</td> 可以：组合遵循 GPLv3</td> 可以：组合遵循 GPLv3+</td> 不行</td></tr>
AGPLv3</td> 可以：组合遵循 LGPLv3</td> 可以：组合遵循 AGPLv3</td> 可以：组合遵循 AGPLv3</td> 不行</td></tr>
AGPLv3+</td> 可以：组合遵循 AGPLv3</td> 可以：组合遵循 AGPLv3</td> 可以：组合遵循 AGPLv3+</td> 不行</td></tr>
</tbody></table>
3. 非 GNU 许可证与 GNU 许可证的兼容性</a>
 #</a>
</h3>
横列表示要并入的代码使用的许可证，纵列表示当前项目的软件许可证。</p>
⬐</th> MIT / BSD 许可证</th> Apache 许可证 2.0</th> MPL 2.0</th> MPL 2.0 NCE</th></tr></thead>

LGPLv2.1</td> 可以</td> 不行</td> 可以</td> 不行</td></tr>
LGPLv2.1+</td> 可以</td> 可以：组合遵循 LGPLv3</td> 可以</td> 不行</td></tr>
LGPLv3</td> 可以</td> 可以</td> 可以</td> 不行</td></tr>
LGPLv3+</td> 可以</td> 可以</td> 可以</td> 不行</td></tr>
GPLv2</td> 可以</td> 不行</td> 可以</td> 不行</td></tr>
GPLv2+</td> 可以</td> 可以：组合遵循 GPLv3</td> 可以</td> 不行</td></tr>
GPLv3</td> 可以</td> 可以</td> 可以</td> 不行</td></tr>
GPLv3+</td> 可以</td> 可以</td> 可以</td> 不行</td></tr>
AGPLv3</td> 可以</td> 可以</td> 可以</td> 不行</td></tr>
AGPLv3+</td> 可以</td> 可以</td> 可以</td> 不行</td></tr>
</tbody></table>

Claim Boilerplate Translations #</a> </h2>
Translations on the example claim on an XMPP account written in English</a>.</p>

Two Weeks of Learning Toki Pona

Sound System Setup for Acoustic Guitar Recording and Streaming

Issues with the English Version of the Mulan Public License

Conclusion #</a> </h2>
While I've certainly got a lot more to talk about, I'm already tired of writing at this point. The steward could have been more professional.</p>

This page is released into the public domain under CC0 1.0</a>.</p>

混合作品的版权归属与许可证兼容性

Hayden's Personal Site

Moving Away from My Home-brew SSG

Presence, Claim and Identity

Hayden's Personal Site

Moving Away from My Home-brew SSG

Presence, Claim and Identity

Claim Boilerplate Translations #</a> </h2> Translations on the example claim on an XMPP account written in English</a>.</p>

Two Weeks of Learning Toki Pona

Sound System Setup for Acoustic Guitar Recording and Streaming

Issues with the English Version of the Mulan Public License

Conclusion #</a> </h2> While I've certainly got a lot more to talk about, I'm already tired of writing at this point. The steward could have been more professional.</p> This page is released into the public domain under CC0 1.0</a>.</p>

混合作品的版权归属与许可证兼容性

Claim Boilerplate Translations #</a> </h2>
Translations on the example claim on an XMPP account written in English</a>.</p>

Conclusion #</a> </h2>
While I've certainly got a lot more to talk about, I'm already tired of writing at this point. The steward could have been more professional.</p>

This page is released into the public domain under CC0 1.0</a>.</p>