In a lengthy interview in Fortune magazine, Microsoft general counsel Brad Smith outlined Microsoft's contention that they can prove 235 patent violations by open source software. And they'd like to be paid royalties, please.
Smith broke down the alleged patent violations during the Fortune interview, saying the Linux kernel violates 42 patents and the operating system's user interface violates a further 65. He went on to claim that the Open Office application suite violates 45 patents and open-source e-mail applications infringe on 15 more. Other open-source software applications infringe on 68 patents, Smith said.
The short answer here is Microsoft owns a lot of patents now, and they're farming them for potential income like any other asset. Novell's licensing deal with Microsoft and Dell's flirtation with the partnership makes sense in one context: it keeps you out of court.