There are lots of as Rob Enderle points out, TomTom can hardly afford to defend itself, anyway:and,
TomTom, which hasn't exactly been an open source poster child, has a problem....Tom Tom really doesn't have the resources to defend against an IP infringement attack during what is likely to be an ugly revenue year. It recently warned that it probably won't be able to repay creditors -- it took a 989 million euro fourth-quarter loss -- and doesn't appear to have the money to pay anyone at the moment. (How it will rigorously defend itself against Microsoft with no money will be interesting to watch).
As Enderle points out, TomTom could be using the vociferous (and often anti-Microsoft) open-source community to fight a public relations battle for it, so that it won't have to engage in costly litigation. It won't work. The open-source community is smart enough to not allow itself to be someone else's pawn.
Ultimately, Microsoft is suing because it believes TomTom violates its patents, with the primary concern being TomTom's GPS patents, not those related to Linux. It's probably time for the open-source world to acknowledge that Microsoft has other priorities that don't involve killing open source, however much that may be part of some Microsoft veterans' strategic vision.
Follow me on Twitter at mjasay.