As I wrote below, yes, somehow missed the news about JVM, but the thing is, as an example, MySQL is GPL'd too and it is not quite open (and I still don't get it how they managed to take GPL down that way).

As far as I know, they keep a dual license; every change in the code goes for both licenses, excepting those changes they want to keep closed, those going only for the non-GPL license. Only the real owner of the software (not the licensee) has the right to do this kind of stuff with GPL.

Please correct me if I'm wrong in my guess.

You got it right. http://forge.mysql.com/wiki/Code_Contributing_FAQ has more information.

Other companies with a split proprietary/free model require copyright assignments for contributions as well. So, too, does the FSF, although for rather different reasons.

Just checked their web site - you are right.