In a letter to SCO released Wednesday, Novell asserted that it retains Unix patents and copyrights, demanded that SCO reveal where Unix source code has been copied into Linux, and raised its own threat of legal action to compensate for damage that it says has been done to customers, programmers and companies using Linux.

"To Novell's knowledge, the 1995 agreement governing SCO's purchase of Unix from Novell does not convey to SCO the associated copyrights," Novell Chief Executive Jack Messman said in the letter to SCO Chief Executive Darl McBride. He said that SCO evidently realizes this, because "over the last few months you have repeatedly asked Novell to transfer the copyrights to SCO, requests that Novell has rejected."

But SCO Group said that that issue is beside the point, because the company bought full rights to the Unix intellectual property, including its copyrights, patents and the right to enforce those patents, according to Chris Sontag, head of the SCOsource effort to derive more money from the Unix intellectual property.