There is no problem solved by this license that is not solved better and more cleanly by a competing license.
Here is the Preamble of the licence:
This turns out to be misleading. We recommend this license for the dustbin.
The FreeDocumentationLicense has a few shortcomings when it comes to wikis. It is complicated by lots of paragraphs that have no meaning in the wiki context (front-cover, back-cover, history, invariant sections). These can all be ignored, but it still makes for difficult reading. At the same time, there are some difficulties when it comes to some of the requirements in environments without a perfect AuditTrail (such as KeptPages expiring, and people reworking pages such that attributions get lost).
The FDL is neither short nor simple. The more you read it, the more you realise how deeply inappropriate it is for any purpose, so this is probably in the FSF's interests.
Troublesome sections of the GFDL for wikis include, but are not limited to: "Secondary Sections", "Invariant Sections", "Cover Texts", "Title Page", license must be included (not linked to), rename modified versions, list authors and publishers, preserve and add copyright notices, "History", "Acknowledgements", "Endorsements" and "Dedications" sections, network locations related to the document, distinction between collections, aggregations, and derivative works, what is verbatim copying, ...
If your wiki content is licensed under the Free Documentation License, then it is suggested that you link to this page, or a similar page, explaining how the license applies to the wiki. However, avoid the error of assuming that your explanation is either accurate or binding.
Here are the basic facts, the stuff that is in the Preamble:
A "Secondary Section" is one that is OffTopic, and which "deals exclusively with the relationship of the publishers or authors of the document to the document's overall subject". For example, a GoalStatement, NamePage?, FrontLawn, etc. "Invariant Sections" are secondary sections protected from changes - most GFDL wikis avoid these like the plague.
Most GFDL Wikis have no "Cover Text", no "Acknowledgements", no "Dedications", and no "Endorsements" section - they could do, but your life will be dramatically easier if you don't. You may want to prevent people from creating a new Wiki page with one of these special cases as title.
The license may require a Title Page and a History page, if you copy your wiki from somewhere else. You'll probably want to use a static page for these required sections, with automatically generated updates after each edit.
A copy of the Free Documentation License must be available from the same server ("include an unaltered copy"). This is necessary so that the license can be read, even if the original gnu.org site goes down. The license does not have to be a wiki page (editing it would be a breach of copyright, anyway).
A "Transparent Copy" of the wiki is usually an archive of the page database, and should include a copy of the wiki engine. This is the file that should be available from a CD ROM if the wiki is ever published as a book, for example. The generated HTML can also be considered Transparent, provided it has not been obfuscated.
It makes things easier if the founder of the wiki is considered the sole "principal author" of the document. Most contributions therefore "modify" the Document created by the "principal author". If the founder did the SeedPosting, this might work, but it's open to interpretation by the courts, who might rule that there are multiple principal authors.
It probably makes things a little easier if you consider the "Document" is not any single page on the wiki, but the entire collection of pages.
The founder of the wiki is usually the same person that pays for the domain name, pays for the hosting, and therefore the founder can be considered the "publisher". Alternatively, the wiki itself could be considered the publisher.
If a wiki doesn't maintain a list of authors besides the founder, then one can assume that the authors have implicitly waived their right to be named in derivative works, so you do not need to actually maintain a list of contributors. This works right up to the point that one of your contributors says that they are not waiving this right, at which point you have problems.
There is no perfect way to prevent identity fraud, on a wiki, or anywhere else, online or offline. Still, there are things people can do - mailing yourself a copy of your text via registered mail, for example, or some form of authentication. On a wiki without full VersionHistory, this is more important.
None of the contributors lose the copyright to their works, even though they are not listed as authors, and their name is not part of the copyright notice. All they do is license their contribution under the Free Documentation License. They may publish their text under another license elsewhere - the GFDL is non-exclusive.
Here is how to interpret the problematic part of section 4. of the Free Documentation License ("MODIFICATIONS"), when making one edit to one page. Compare this to the complexity of just hitting "EditThisPage" on a normal non-GFDL wiki.
Note the problem of the ballooning "History" section: If your wiki has been edited a thousand times, you'll have a history file with a thousand lines in it, and you must now this history section on your back forever. If you print off a copy of a page, print off the thousand lines of history. If you fork, take a copy of the thousand lines of history. There's no way to trim this monster: it just gets bigger and bigger and bigger, one line for every edit.
Fortunately, you can avoid the problem of the ballooning "History" section (and others): Instead of saying that contributors edit the document, say that the contributors grant permission to the publisher to publish their work under the GFDL. This means that rather than lots of little piddly modifications, there is one single modification, performed by the publisher on any source GFDL documents. Thus, you need your contributors to grant a LicenseToLicense?.
Here is how to interpret section 4. of the Free Documentation License ("MODIFICATIONS"), when publishing a copy (a mirror or a fork) of the wiki.
When copying a piece of text from a wiki licensed under the Free Documentation License, me must look at the intent of the license. There are no precise intructions in the license. We cannot interpret this as a modification followed by a combination, because the modification would not allow us to remove the Title Page and the History section, for example.
Going back to the preamble, the purpose is to keep the modifications "free", and to give credit to authors and publishers. To keep it "free", we must require that the target document -- the document where the piece of text is copied to -- is also "free". In fact, our safest bet is to require that the the target document be licensed under the Free Documentation License.
There are no exceptions, unless all the original authors of the text being copied agree to license the text under some other condition in addition to the Free Documentation License. Note that the wiki software will usually not be able to tell you who all the authors are, so you are taking a legal risk, when you do that.
As to giving credit: The source wiki already does not guarantee credit for authors (see above for more about authorship), so it is obviously impossible to give credit to authors in the target document. The license gives publishers the ability to add Invariant sections as well as a Front and a Back Cover section. Since a wiki does not have these sections, there are no additional requirements.
Summary: You can copy a piece of text from a wiki licensed under the Free Documentation License, if and only if the target document is also licensed under the Free Documentation License.
You can consider that the source wiki is a collection of documents (under section 6) and "extract" a single page as a single document. This allows for the above approach, but is legally iffy.
Alternatively, you can take the whole wiki and create a modified version by deleting everything you don't want to copy. But you have to keep the title page and the full history page (even though most of it won't be applicable). So this is less good.
You could also take advantage of RichardStallman's and JimboWales?'s position on aggregation and consider that you are simply creating an aggregation of your (AllRightsReserved?) text with the single GFDL'd piece of text you want to copy.
FairUse is not the answer, by the way. There is a pretty clear definition for "fair use" in the various copyright laws. In short: You may quote parts of a work, if and only iff the quote is just a part in the context of an independent work that talks about or refers to the quote.
Here is a typical problem in this context. Note that the sort of maintenance suggested in the example should be unnecessary.
"I've seen some definitions for terms on another website that was licenced under the FDL. I want to have a lot of definitions of similar terms on a wiki I'm involved in (AIWiki); there is significant overlap but what the two sites want to define is not identical. I would like to just copy the definitions for the terms that we are using at AIWiki over, however, I think manually maintaining a list of which parts of all AIWiki pages are `contaminated' by FDLed content may be too burdensome."
Since the wiki accepts contributions from everybody, the publisher might be considered responsible for copyright infringements. Usually, however, publishers are not held responsible for content on their sites, if the sheer volume of new material exceeds the capabilities of the publisher. Furthermore, if publishers remove offending material upon receipt of a notification (eg. a cease and desist letter), then there is usually no case to be made against them. If the publishers can convince them that removing the offending material themselves while leaving an explanatory note, then the problem can probably be settled peacefully and outside of court.
There is, however, no 100% protection for publishers. If somebody is losing a lot of money because of some copyright infringement happening on the wiki, then they could try to sue you for damages. Whether you will be found guilty will depend on how accessible the original material was, how diligently you checked for copyright infringements, how much other material was getting posted at the same time, etc. In the end, there are no guarantees.
The wiki should probably carry a warning for potential publishers that want to excercise their rights; something that warns them in all fairness of potential copyright infringements, and informs them of the legal risks they are taking when publishing the material.
The wiki should probably also carry a note for potential contributors, asking them to only contribute material that does not infringe on any copyrights: Either by making sure they only contribute their own work, or by making sure they ask the original authors wether they would license their work under the Free Documentation License.
Note that you can't without using a LicenseToLicense?, because Usemod doesn't have the tech to do the automatic updating of history pages, title page, etc.
The FooterNote holds the text that gets displayed at the bottom of every page. Set it as follows:
$FooterNote = "Permission is granted to copy, distribute and/or
modify this document under the terms of the <a
href=\"http://www.emacswiki.org/FDL\">GNU Free Documentation
License</a>, Version 1.2 or any later version published by the <a
href=\"http://www.fsf.org/\">Free Software Foundation</a>."; # HTML
for bottom of every page
The EditNote holds the text that gets displayed before the Save button on edit pages. Set it as follows:
$EditNote = "By contributing to this wiki, you grant us the normal implicit license to mercilessly edit your text. Further, you grant us the right to licesnse the result under the <a
href=\"http://www.emacswiki.org/FDL\">GNU Free Documentation
License</a>. Please only contribute your own original work."; # HTML notice above buttons on edit page
And wherever you make the page database and the wiki script used available for download, print:
DISCLAIMER OF WARRANTY OF TITLE: Please be aware that the page database may contain copyright
infringements. Should you decide to publish it, you may be held
responsible for these infringements.
The one major problem with the GFDL, other than its ambiguity as to what defines the Document when talking about a website, is its inclusion of Invariant Sections. As has been pointed out at the GFDL comment page at gnu.org, Invariant Sections make the GFDL incompatible with the GPL, which is a major pain. Invariant Sections lead to a host of problems, in fact. Otherwise it's quite good, and does fit quite well with wikis. The one important thing that should be done to ensure compliance is to make sure (and this would be great if someone enfolded this functionality into the software) that there is a History section, as defined by the GFDL, which keeps track of the documents (and their authors) sourced by the wiki. But I can certainly sympathize with such a stripped down license as the FWL. I suspect it could be even shorter.