This is not about any patents against Linux or whatever. Microsoft just tries to discredit everything that has to do with Linux in general. They want to create a level of uncertainity in people's minds about Linux so they have concerns about the legal status of the OS. If people are in doubt, they might favour Windows since there they know that they've paid for something "absolutely legal".

It would be interesting if some megacorp digged up and bought out all the patents that Microsoft ever violated ... and would come up with a thousand patent infringement suits. :->