Anthony DiPierro wrote
- The verbal agreement Jimmy and I made was that I would continue to
retain copyright to software contributions I make during my employment.
Copyright assignment must be in writing. If you really care about this, well, you can figure out what to do. Of course it almost surely doesn't matter.
Copyright assignment does not have to be in writing. In this case, it would in many ways (particularly because Brian was contributing before employment by the Foundation) have to fall on the Foundation to prove that they own it. A written agreement in this case, however, would have more legal merit. E-mail logs like this where Brian claims copyright and is not disputed by anybody on the Foundation board like Jimbo could also be a claim on copyright in that regard because Brian's contributions are certainly not in doubt that he actually wrote some of the software in MediaWiki.
It is irrelevant anyway as this is a GPL'd piece of software and in the situation with copyleft software both the Foundation and Brian acting as an individual would be co-owners seeking to enforce provisions of the GPL if they choose to (like somebody selling a propritary version of MediaWiki and not disclosing source code and other details required by the GPL). It would be for purposes of GPL enforcement that it might be desireable to grant copyright assignment to the Wikimedia Foundation anyway, just like the Free Software Foundation suggests that GNU software have the copyright assigned to them for GPL defense issues as well. If you don't "own" the software or literary work, you can't defend the copyright.
That is where the Wikimedia Foundation may be in some trouble with Wikipedia content as there are several places where the Wikimedia Foundation disclaims any copyright to content on Wikipedia and other Wikimedia projects. The Foundation really can't enforce a provision of the GFDL as a result if they don't have copyright ownership on any of the material.