It sure seems like a good time to be a lawyer specializing in patent law, as we keep seeing companies, unable to reach licensing terms amicably, take each other to court over claims of patent violations. First there was Apple and its claim over many of the methods used to interact with a multi-touch display. The company is using its patents against Palm, which it claims violates them with its upcoming Pre smartphone.

The latest case concerns Microsoft and GPS navigator-maker TomTom. Microsoft holds several patents related to GPS systems that it says TomTom is violating, but that's not what makes this case so serious. Some of the patents Microsoft is enforcing are applicable to nearly every device running a version of the open-source Linux operating system. Further attempts to enforce these patents, if held up by the courts, would be disastrous for the free OS.

One of the patents in question deals with long file name support. When Microsoft introduced Windows 95, it designed a system to add support for file names longer than 11 characters while still having backwards compatibility with old files. In order to correctly work with such file systems, Linux needs to support the same protocol. Luckily the courts have already invalidated the patent once before, but Microsoft was able to have it re-certified later. This means it's already going to be viewed by the courts as being on shaky legal ground, and perhaps won't stand up to a second round of inquiry.

To be fair, there's no indication that Microsoft has the open-source community targeted with threats of legal actions over similar patent claims. It looks like TomTom just made the company mad by refusing to license its navigation system patents, so it threw the book at TomTom, including any and all patent violations its lawyers could drum up. If the courts use this opportunity to once again invalidate the long file name patent, that could be a bad move on Microsoft's part. For now, though, open-source advocates are keeping a cautiously watchful eye on the case.

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