A user of the German Wikipedia, Ulrich Fuchs, has threatened to take legal action against any third party who makes commercial use of their material without following a very narrow interpretation of the FDL "five author" requirement, which reads as follows:
"B. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement."
Our recommendation for third parties using Wikipedia material so far has been that it is completely sufficient in the spirit of the FDL to point to the original Wikipedia article on which the copy is based, because that page contains the history and therefore the list of *all* authors. Ulrich claims that this is not sufficient because it does not meet the conditions of modification set forth in the FDL.
This is not just theoretical. There is a new commercial German project called "Flexicon" which uses Wikipedia material. Currently they don't give any credit whatsoever, but since Flexicon itself is a wiki, some Wikipedians have added links to the original Wikipedia articles in order to meet the conditions of the FDL. Ulrich now threatens anyone with legal action who copies material to Flexicon from the German Wikipedia which he has worked on without having the unworkable "list of five principal authors" on the target page.
This would place an unacceptable burden on third parties as they would have to carry along the complete history of every page thtey use (since there is no automated way to determine who is a principal author), a history which on the English Wikipedia is now so large that we can't even store it in a single file anymore (over 2 gigabytes). Not to mention that having such a list in articles is cumbersome and annoying.
In my opinion, legal threats like these are dangerous to this project and to the very idea of open content. They also show once again that the FDL is a fundamentally flawed, overly complex license with lots of loopholes for pedants who want to get their way instead of working with the community.
There may be a solution to prevent this problem from escalating. We could amend the edit notice on Wikipedia to require the author to release third parties from the need to maintain a list of five "principal authors" per page, since such a release is explicitly provided for in the FDL..
Regards,
Erik