Why (non-mandatory) copyright assignment
Chris Webber on "Why copyright assignment?":
GNU MediaGoblin is a GNU project with non-mandatory but heavily encouraged copyright assignment to the FSF. Most, if not all, of the core contributors to GNU MediaGoblin will have done a copyright assignment, but unlike some other GNU projects, it isn't required here. We think this is the best choice for GNU MediaGoblin: it ensures that the Free Software Foundation may protect the software by enforcing the AGPL if the FSF sees fit, but it also means that we can immediately merge in changes from a new contributor. It also means that some significant non-FSF contributors might also be able to enforce the AGPL if seen fit.
Again, assignment is not mandatory, but it is heavily encouraged, even incentivized: Significant contributors who do a copyright assignment to the FSF are eligible to have a unique goblin drawing produced for them by the project's main founder, Christopher Allan Webber.<ref> contributing-howto</ref>