A group of Linux proponents will purchase patents formerly held by Microsoft in an effort to defend distributors of the open-source OS against the ongoing threat of patent litigation from the software giant.

The Open Invention Network (OIN), whose members include IBM and Red Hat, is set to purchase a set of 22 patents once held by Microsoft from Allied Security Trust (AST). They include Linux patents marketed and sold by Microsoft, some of which were previously held by Silicon Graphics, said Keith Bergelt, CEO of OIN, in an interview Tuesday.

AST was founded by a group of technology companies to purchase patents to protect interested parties from patent litigation. Its members include Hewlett-Packard, IBM and Verizon. The AST acquired the patents in a private auction held by Microsoft, one that OIN was not permitted to participate in, Bergelt said.

OIN, a not-for-profit company that also counts Sony, NEC, Novell and Phillips as members, purchases patents that pertain to technologies found in open-source software to protect the open-source community from patent litigation from so-called "patent trolls," he said.

Patent trolls, known more formally as non-practicing entities (NPEs), are companies that exist merely to own patents so they can sue companies for violating them.

"If they get access to these [patents] they would then go about suing, which creates a perceptual issue around Linux that's highly inaccurate," he said. "It represents a potential source of antagonism and source of FUD (fear, uncertainty and doubt) for the community."

Patent trolls are not the only companies that seek patent royalties from open-source companies, however.

Microsoft has a storied rivalry with Linux and has been quietly striking deals with companies that distribute Linux or components of it to license technology in the OS for which Microsoft claims to hold patents.

Microsoft executives have said that Linux violates more than 235 patents the company holds, a claim open-source proponents have refuted.

Bergelt said Microsoft was not OIN's target in purchasing the patents.

"Most of the statements that Microsoft has made with regard to patents and Linux have been to generate FUD," he said.

"Non-practicing entities, for the most part, thrive on lower-quality patents in the hopes of generating quick returns. OIN’s objective was to remove access to these patents from the NPE community."

Microsoft usually strikes patent deals with companies before bringing cases to court, but a case earlier this year against GPS navigation device vendor TomTom, which uses Linux in its devices, was a notable exception.

TomTom eventually agreed to pay Microsoft to settle the case, which Microsoft insisted was a mere patent disagreement rather than an attack against Linux.

Not all Linux and open-source proponents felt the same way about it, however, though most open-source companies -- which are much smaller players than Microsoft -- would rather pay the proprietary software company to protect themselves against litigation than try to fight its deep pockets in court.

"With the current patent system in place, it is to be expected that various parties with competing interests will continue to acquire patents and patent portfolios for defensive purposes, if nothing else," said Stephen O'Grady, an analyst with Red Monk.

O'Grady said that until more is known about what is covered in the patents OIN is purchasing, it's "impossible to assess the implications" of Tuesday's move.

However, if the group is going through the trouble to acquire them, "presumably they at least believe they will be useful to Linux, either offensively or defensively," he said.

Bergelt said OIN plans to post the patents on its Web site by the close of business Wednesday.