The goal of this page (which is open to redefinition, since all are encouraged to edit) is not to supplant any debate on Wikipedia-L but to complement it by directly analyzing the nuances of the GFDL as they may apply to Wikipedia.
Note: at present (October 28), the following is written by a single Wikipedian, The Cunctator, edited in two instances by SJK, and now with this comment by LMS. The fact that it is written mainly by one person does not, of course, mean that it is necessarily a biased presentation of the issues. But please be aware that this does not represent an "official workshop" on the issues raised by the page. In particular, please be aware that these issues have been discussed publicly by many other people, and will continue to be discussed in the near future, on Wikipedia-L; please see the relevant mailing list archive to see how this debate has proceeded. --Larry Sanger
Required copyright and license notice 
The GFDL requires use of a copyright and license notice. Here are possibilities for their use.
Everyone who contributes to Wikipedia is a copyright holder. The only way we could change this would be for each person to legally assign their copyright. So we should simply say something like "Copyright © 2001 Wikipedia Contributors". See also Authors below.
To get each person to legally assign their copyright to a single entity for what has already been written is essentially impossible. But in the future, authors could be asked to assign copyright to some entity upon submission.
However, there is also compilation copyright.
License notice 
The parts that can be varied are in italics.
1. The least restrictive version of the copyright and license notice.
Copyright (C) 2001 Wikipedia Contributors. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled ``GNU Free Documentation License.
2. Requiring a link-back:
Copyright (C) 2001 Wikipedia Contributors. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with the Invariant Sections being link.html, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled ``GNU Free Documentation License.
However, requiring a link-back may be redundant, because compliance with the GFDL requires a "publicly-accessible computer-network location" of a "transparent" copy of the document.
Modified versions have to include a network location for previous versions unless they're a modification of a version which is more than four years old.
In other words, people already pretty much have to link back to Wikipedia.
Secondary Sections 
The only sections which may be designated as invariant are those which are secondary; which means that they "contain nothing that could fall directly within that overall subject." See Questions below.
Other Sections 
The License defines particular sections
Optional, but if included in the original, the substance and tone of the acknowledgements must be preserved in modified versions.
Optional, but if included in the original, the substance and tone of the dedications must be preserved in modified versions.
Title Page 
"the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text"
In modified versions, it is necessary for the Title Page to include the names of the principal authors; and for the History section to include the title, principal authors, and publisher. Thus, we need to clearly define title, authors, and publisher.
This is the publication history of previous versions, only necessary in modified versions. See title, authors, publisher.
Optional, but this section cannot be included in modified versions.
What we consider to be the title should be explicitly defined. Is it HomePage? Wikipedia?
Or are we asserting that each entry is separately released under the GFDL, so that the title of an entry may be considered as the title for the purposes of GFDL compliance?
To allow people to publish modified versions in compliance with the GFDL, we need to add some commentary to define what we consider to be the primary authors.
- "There are no primary authors."
The publisher must be explicitly mentioned for people to successfully meet the requirements of the License. In particular, the publisher must be mentioned on the History page. Also, the GFDL states the publisher may grant certain permissions (see below).
Mechanism for Granting Optional Permissions 
The GFDL explicitly states that the publisher and authors may grant certain permissions not automatically granted by the License; they include:
The publisher may grant these permissions:
- Publishing a modified version with the same title as the original
- Omitting a network location for public access to a "transparent" copy of the original
- Replacing cover texts originally added by the licensee in an earlier modificatication
The copyright holders may grant this permission:
- Replacing Invariant Sections with translations
Q. What exactly is being released under the GFDL? 
Are we releasing the entire Wikipedia.com site, the whole tarball, under the GFDL, or are we also releasing each individual entry under the GFDL?
Factors in releasing only entire site:
- It's a lot simpler for us.
Factors in releasing individual articles:
- Makes reuse much easier for others
- Thus, increases GFDL "infection"
- There is little or no difference here. If you release each individual article under GFDL, you can combine them (the GFDL has provisions dealing with the combination of separate documents into one document). If, on the other hand you release the whole site under the GFDL, then you can always delete all but one article to make a Modified Version. -- SJK
1. There's actually a major difference, because you can have different invariant sections, cover texts, and other sections if you have different license set-ups. Thus, the whole Wikipedia could have a set of invariant sections/cover texts etc. that the individual entries do not.
More specifically, certain pages (like the HomePage) could have more ancillary materials than the average entry.
2. Another major difference: if the entries are released individually under the GFDL, you can copy them individually under the Verbatim Copying clause; if the License covers all of Wikipedia, then doing that would fall under the Modifications clause.
3. Another major difference is perhaps (we need a legal expert to answer this) Wikipedia can have a compilation copyright holder, while individual entries have the Wikipedia Contributors copyright holder. Fortunately, the GFDL obviates most need to deal with copyright holders; just about the only one the publisher can't handle is that Invariant Section translation issue. It would be a good idea to resolve that explicitly (perhaps by not having Invariant Sections).
There will probably be a few major instances of reuse for Wikipedia:
|Instance||Entries licensed individually||One single licensing|
|1. Copying an individual entry||verbatim copying||A modification of the whole entity|
|2. Copying from an individual entry||modification of single entry||A modification of the whole entity|
|3. Using Wikipedia as a database||Combining documents||A modification or verbatim copying of whole entity|
|4. Putting parts of Wikipedia into book form||Combining documents||A modification of the whole entity|
Note especially the difference in #1, which is important, because that is the predominant use of Wikipedia by individuals.
How do translations of English Wikipedia articles for other language Wikipedias need to be handled? 
Right now, it's being handled informally, pretty much assuming that all the Wikipedias can share and share alike, and people should give references. In the future, it would behoove us to ensure that we are in compliance with the Translation section (#8) of the GFDL. What will be necessary to do that depends on how exactly we implement the license.
Is there anything on Wikipedia which can't fall directly within the overall subject of Wikipedia? 
The only sections which may be designated as invariant are those which are secondary; which means that they "contain nothing that could fall directly within that overall subject."
What is the overall subject of Wikipedia? While the answer isn't directly answered, from Wikipedia policy: "Wikipedia is an encyclopedia". From encyclopedia: "an encyclopedia is a written compendium of human knowledge." So we may reasonably infer that the overall subject of Wikipedia is "human knowledge."
One amusing paradox is whether the pages about Wikipedia (e.g. Wikipedia policy) fall directly within the overall subject of Wikipedia. In a certain real sense, pages about Wikipedia (including Wikipedians and individual Wikipedian pages) fall directly within human knowledge.
But this sense is certainly stretched to its limit when one considers most /Talk pages.
It would be similarly unreasonable to consider a required link to Wikipedia to directly fall within the overall subject.