"A once-bitter rival of Microsoft and creator of the SUSE Linux distribution that competes with Windows, Novell..."

Someone who writes for Computerworld ought to know that Novell most certainly did NOT create the SuSE Linux distro.

As for using the intellectual property of another party without consent, this much more typifies Microsoft than it does the open source community. I suspect Ballmer is simply taking the strategy, "The best defense is a good offense." I would not be at all surprised to learn that Windows Vista uses much more Linux/UNIX code than Linux/UNIX uses Windows code.

I doubt that Microsoft is suggesting that there is Windows infringing code in the Linux kernel at all. After all, Linux was modelled on Unix, and that predates Windows by a good margin.

I'm sure what they are getting at is that they see projects like Samba and Mono to be infringing. Those are projects which are designed to enable interoperability and cross platform development or deployment.

Interoperability: that's that thing that Ballmer says he wants to help his customers with. It's also the very thing he is being sued by the EU to allow. And here's Microsoft's version: if you pay Microsoft, they won't sue you when you try to achieve it.

The reason why Microsoft does not have a history of pursuing patent litigation is they are too busy ripping of everyone else's IP, and don't want to upset the apple-cart (pun intended). However, given the number of patents registered by MS lately, any down-turn in market share could change all that very quickly.