It's all about patent protection, but ironicaly, Microsoft is not going to sue anyone over patents. Microsoft execs know that if they did this the various organizations that have a stake in the success of Linux (which is essentially everyone but Microsoft) would pay for a well-funded defense. Millions of dollars would be spent, and in the end the patents in question would either be shot down or removed from the Free Software product in question. Depending on who Microsoft chose to attack it could even trigger retaliation from other large players with huge patent repositories. What's more, Microsoft's patent aggression would start a wholesale migration away from Microsoft's technologies. And why not analyse the 50 millions of Windows source code, in order to see if Windows do not infringe or has copied any linux code? Overalll the release of Java under a GPL licence is a great step against the monpolistic pratice of Microsoft. Java can now never be takeen down or disapear during an hostile aquisition.