In the U.S. District Court in Seattle, Microsoft sued TomTom (PDF Link) on the ground that TomTom's in-car navigation devices violate eight of its patents. At least three of these patents, concerning file management, reference TomTom's Linux kernel implementation.
This is the first time that Microsoft has ever filed a Linux patent suit over Linux, despite its multiple claims. That said, according to Todd Bishop, "Microsoft says open-source software is not the intended focal point of the action."
In the past, Microsoft has supported legal action against Linux. Microsoft infamously funneled money to SCO to fuel its lawsuits against IBM and other Linux-using companies. With SCO's complete failure to even prove that it had any rights to Unix, never mind Linux, there was no longer any even half-credible legal actions against Linux.
It's also worth noting that while Microsoft has often threatened Linux-related companies, Microsoft has recently made alliances with them as well. This started in 2007 with what has turned into into a close partnership with Novell. More recently, Microsoft partnered with Red Hat.
Bishop also reported that, "Microsoft says it filed the case as a last resort, after trying for more than a year to reach an agreement with TomTom." Horacio Gutierrez, Microsoft corporate vice president and deputy general counsel for intellectual property, also told Bishop that, Microsoft would be happy to quickly resolve the TomTom dispute by a license.
So, which is it? It Microsoft actually starting a legal attack against Linux? Is this just a routine IP licensing dispute that happens to touch on Linux? At this point, we don't know. Even Eben Moglen, co-author of the GPLv3, open-source's core license, tells me he's not sure what the lawsuit means yet.
We're just going to have to wait and see what Microsoft's lawsuit is going to mean to Linux.