GFDL

GFDL，可以譯 GNU 自由文章授權條款，係一個由自由軟件基金會為 GNU 計劃而設計嘅一套反版權授權條款，特別係設計來畀自由文件用，對應 GPL 授權條款。同 GPL 一樣，佢係設計到讀者有權複製、分發同修改 GFDL 授權嘅作品，而且無論係直接複製抑或二次創作嘅作品，都一定要用一樣嘅條款授權。抄出來嘅複製品亦都准賣，但係如果印得多，賣嘅時候就一定要跟埋原作或者作品源碼。

GFDL 本來係設計來畀說明書、課本｢次要部分｣ 
喺呢套條款之下，所謂 ｢文件｣同所謂 ｢次要部分｣有清楚嘅劃分。所謂次要部分，係指未必整合咗入正文，但係同正文有關嘅嘢，例如印刷業所講嘅正文前部同結文，次要部分可以包括例如作者資料、出版者資料等等同正文主題冇直接關係嘅嘢。｢文件｣可以隨便改，但係次要部份反而可能有特別嘅限制，目的係確保之前嘅作者唔會無端端冇咗名等等；另外，正文嘅修改條款雖然同 GPL 對應，但係 GFDL 同 GPL 並唔兼容，GPL 同 GFDL 亦都唔兼容。

Specifically, the authors of prior versions have to be acknowledged and certain "invariant sections" specified by the original author and dealing with his or her relationship to the subject matter may not be changed. If the material is modified, its title has to be changed (unless the prior authors give permission to retain the title). The license also has provisions for the handling of front-cover and back-cover texts of books, as well as for "History", "Acknowledgements", "Dedications" and "Endorsements" sections.

商業再分發 
GFDL requires the ability to "copy and distribute the Document in any medium, either commercially or noncommercially" and therefore is incompatible with material that excludes commercial re-use. Material that restricts commercial re-use is incompatible with the license and cannot be incorporated into the work. However, incorporating such restricted material may be fair use under United States copyright law and does not need to be licensed to fall within the GFDL if such fair use is covered by all potential subsequent uses.一個例子係of such liberal and commercial fair use is parody.

對GFDL嘅批評 
The Debian project and Nathanael Nerode have raised objections. Debian developers eventually voted to consider works licensed under the GFDL to comply with their Debian Free Software Guidelines provided the invariant section clauses are not used. These critics recommend the use of alternate licenses such as the share-alike Creative Commons licenses, the BSD Documentation License, or even the GNU GPL. They consider the GFDL a non-free license. The reasons for this are that the GFDL allows "invariant" text which cannot be modified or removed, and that its prohibition against digital rights management (DRM) systems applies to valid usages, like for "private copies made and not distributed".

反數碼權利管理反得過咗火 
The GNU FDL contains the statement:

A criticism of this language is that it is too broad, because it applies to private copies made but not distributed. This means that a licensee is not allowed to save document copies "made" in a proprietary file format or using encryption.

In 2003, Richard Stallman said about the above sentence on the debian-legal mailing list:

唔准改嘅部分 
A GNU FDL work can quickly be encumbered因為a new, different, title must be given and a list of previous titles must be kept. This could lead to the situation where there are a whole series of title pages, and dedications, in each and every copy of the book if it has a long lineage. These pages cannot ever be removed, at least not until the work enters the public domain after copyright expires.

Richard Stallman 講過 about invariant sections on the debian-legal mailing list:

同 GPL 互相唔兼容 
The GNU FDL is incompatible in both directions with the GPL: that is GNU FDL material cannot be put into GPL code and GPL code cannot be put into a GNU FDL manual. Because of this, code samples are often dual-licensed so that they may appear in documentation and can be incorporated into a free software program.

At the2006年6月22號－23號 international GPLv3 conference in Barcelona, Moglen hinted that a future version of the GPL could be made suitable for documentation:

印嘢超麻煩 
The GNU FDL requires that licenses, when printing a文件covered by the license, must also include "this License, the copyright notices, and the license notice saying this License applies to the Document".咁樣表示咗如果一篇文licensee prints out a copy of an article whose text is covered under the GNU FDL, he or she must also include a copyright notice and a physical printout of the GNU FDL, which is a significantly large document in itself.

｢透明｣ 嘅格式 
The definition of a "transparent" format is complicated, and may be difficult to apply. For example, drawings are required to be in a format that allows them to be revised straightforwardly with "some widely available drawing editor." The definition of "widely available" may be difficult to interpret, and may change over time, since, e.g., the open-source Inkscape編輯者is rapidly maturing, but has not yet reached version 1.0. This section, which was rewritten somewhat between versions 1.1 and 1.2 of the license, uses the terms "widely available" and "proprietary" inconsistently and without defining them. According to a strict interpretation of the license, the references to "generic text editors" could be interpreted as ruling out a format used by an open-source word-processor such as Abiword; according to a loose interpretation, however, Microsoft Word .doc format could qualify as transparent, since a subset of .doc files can be edited perfectly using OpenOffice.org, and the format therefore is not one "that can be read and edited only by proprietary word processors."

歷史 
喺 1999 年底，第一份 FDL 草稿出咗，用來搵人畀意見。修改咗幾次之後，2000年3月出咗第 1.1 版，2002年11月出咗第 1.2 版，喺2007年係第 1.2 版。

2006年9月26號，第一份討論用嘅 GFDL 第二版草稿出咗，同時出埋新寫嘅 GNU Simpler Free Documentation License草稿。

新版嘅 GFDL 比舊版好咗好多，例如加入咗 GPL 寫第三版嘅時喺寫嘅新條款，等做國際化易啲，易啲將條款用喺錄音或者影片，節錄用作品嘅時候冇咁麻煩等等。

至於簡化版，就冇咗有關 ｢封面、封底｣同 ｢唔改得嘅部分｣嘅限制，令唔想用爾啲條款嘅作者可以有個簡單啲嘅選擇。

其他嘅自由授權條款 
坊間有其他嘅自由授權條款，當中有啲同 GFDL 完全冇關，第啲就係回應 GFDL 被人覺得寫得差嘅地方。例子包括：
 FreeBSD Documentation License
 共享創意
 Design Science License
 Free Art license
 Open Content License
 Open Publication License

BSD license
 版權
 Copyleft
 Free software license
 GNU
 Open content
 Share-alike
 Software licensing 
 Non-commercial educational

連出去 
 GFDL 條款原文
 GFDL 嘅官方網頁
 Free Software and Free Manuals
 Why Wikivoyage isn't GFDL: Problems with using the GFDL for short printed texts
 The Free Universal Encyclopedia And Learning Resource
 Guide to the new drafts of documentation licenses

自由軟件