This article states that Microsoft is claiming patent infringement. Given the broad brush that corporations used to develop their patent portfolios beginning in the early 1990’s, I would suspect that MS can probably identify a large number of patent infringements. The fact that they are challenging “open source” just makes their job easier.
For a variety of technical reasons, many dispassionate observers suspect that software patents are especially vulnerable to court challenge.
Microsoft asserting this line of reasoning is a Good Thing. IMHO, software patents are a joke and by the time this all washes out, there will be far, far fewer of the absudrdities that are patented today.
But, still waiting for the definitive end of the IBM/SCO lawsuit.