I think I would describe MS’ weapon against open source not as stupidity as Michael Tiemann says, but plain cluelessness in “Yet Another Microsoft Attempt To Be Nice to OSS” (TM).
Without having the EU slap even more fines on them, they can prove to the whole world that they are serious about wanting to work with the FOSS community by doing simple things like signing up unconditionally with the Open Invention Network. All their attempts so far: “share source”, codeplex, etc do not cut it. I guess being clueless is hard to cure, so I reckon they will continue to behaving badly until the EU extracts even more money. Simple formula I think.