Earlier quoted context omitted.
One thing to keep in mind, WordPress being open source was an afterthought. It inherited a GPL from b2/cafelog. If Matt woke up one morning and decided he wanted to make WordPress closed source, he couldn't. But what he could do is force everyone to pay a license fee for the name, and anyone who did not pay he publicly makes hell for them. You could also pretend to encourage them to fork, knowing full well they would…
I don't understand your point about forking, yes they'd have the GPL but so what? They can control their fork from then on, it doesn't matter if they have to continue open sourcing contributions, in fact it'd be preferable to whatever Matt is doing.
I agree with Matt's ideals but not the actions. The reality is theres not a whole lot he can do without looking like spoilt kid taking his ball away from the game.