Schewek wrote:

Why not add a "from <chose your date> the license is changed to...", and ask all contributers to sign on a page if they retroactively agree, and theoretically one could filter out all articles not covered and rewrite those is necessary.

You mentioned articles and not modules so I assume you are talking about Wikipedia. In short: that's impossible on practical grounds. There have probably been more than 20,000 people who have edited Wikipedia and most of them were either anonymous or didn't leave an email address behind that is still active.

Depending on the change many people may also opt not to agree to the change - I would probably be one of those just on the principal that we shouldn't change things like our license arbitrarily (it has worked great so far; so why rock the boat?).

That is still possible for the textbook project though - however most of the content being placed there so far is GFDLd textbooks that were created elsewhere and copied Wikipedia text.

We can discuss the possibility of changing license terms when somebody finds an impressive non-FDLd free text resource whose copyright owner declines our nicely-worded request to grant us a GFDL license of their work.

-- Daniel Mayer (aka mav)