TomTom, the Dutch GPS player that Microsoft sued a couple of weeks ago for patent infringement specifically charging its Linux kernel with offending, has not only countersued, it's lining up allies.

It's joined the IBM-inspired Linux-protecting Open Invention Network (OIN) as a licensee.

OIN holds by its own count more than 275 "strategic worldwide patents and patent applications" - exactly what has never been made public - after the example of mutual deterrence back in the days of the Cold War.

It was formed in 2005 after SCO sued IBM for importing Unix code into Linux.

The patents OIN owns are available royalty-free to any company that agrees not to assert its patents against Linux. It's basically pledged to rattle its patents under the nose of anybody who comes gunning for one of its own, which collaterally brings in the Linux Foundation and the so-called Linux Defenders, the four-month-old patent attack dog OIN and the Linux Foundation sponsor.

When it sued TomTom - and took its claims to the International Trade Commission - Microsoft said it had been after the Dutch company for over a year trying to get it to license its patents, behavior the GPL governing Linux prohibits.

The Microsoft suit is the first time the company has exerted its Linux pretensions in a suit. The suit largely centers on its FAT32 IP.

OIN has gotten investments from IBM, NEC, Novell, Philips, Red Hat and Sony. Google and Oracle are members.