The patent pool being built by the Open Source Development Labs (OSDL) is useless in the defence against Microsoft, according to open source activist Bruce Perens speaking at the LinuxWorld conference in San Francisco.

"The patents come from the wrong people," he said during a meeting with reporters, because only friends of open source will submit to the pool.

The pool also is useless as a defence against patent claims because most of the main patent holders have cross licensing deals with each other.

This means that large companies, including Microsoft, IBM and HP, have agreed to let the others use their patents.

"If Microsoft turns out to be the aggressor, that does not help," noted Perens. "The pool unfortunately turns out to be spitting in the wind."

OSDL unveiled the Patent Commons Project on Tuesday that will build a library of patents that have been pledged to open source including the conditions of that pledge.

The initiative is an attempt to decrease the threat of software patents against open source projects, which is effectively intended to prevent a repeat of the legal action that SCO undertook against Linux.

"You have this skeleton in the closet," warned Perens. "Every open source programme of any significant size infringes on tens or hundreds of patents."