Microsoft's 'on again off again' relationship with Linux is now seems 'off again' after it issued a patent infringement lawsuit against TomTom, maker of GPS systems.

The three charges are all related to Linux file management technologies which are under the bonnet of TomTom gear. However it does not seem that Microsoft is miffed at the Linux in TomTom's package, more the way that the outfit uses the Linux kernel.

In other words it is a normal business dispute between two companies and Linux is not the focal point of the action. TomTom has been in hot water over patents for years and some of them are to do with the way it uses Linux.