Denis-Courmont may have licensed his code under GPL for a reason, but it can very well be a bad, zealous reason. Indeed, I would expect that almost every person who truly is a zealot and a bad apple would choose to license their code under GPL. The GPL is a license that demands total obedience to a particular ideology of software distribution, and requiring that other people obey your ideology in every detail is the defining characteristic of a zealot.
Gee, I don't know. Maybe for the good of the hundreds of thousands of users of iOS/VLC? Maybe because the other contributors had agreed to this and didn't care for the technical violation, especially since both the code was available and the app was free? Maybe because also working for Nokia seems like a huge conflict of interest?
In this particular case, anyone that was already capable of running code they compiled on an iphone (read: people with a developer license) was also capable of making and using modified versions of VLC.