Linux adversary the SCO Group sued rival software maker Novell on Tuesday, alleging that Novell has falsely claimed that it controls the Unix operating system.

The suit, filed in Utah's Third District Court in Salt Lake City, accuses Novell of slander and seeks an order that would require Novell to assign to SCO all Unix-related copyrights and to withdraw any statements claiming ownership of Unix.

SCO rattled the technology world last year when it filed a $3 billion lawsuit against IBM, claiming that the computing giant illegally incorporated into its Linux software source code from the Unix OS, which SCO controls. Novell became an early combatant in the dispute, claiming that it retained certain copyrights when it sold the Unix rights to SCO.

The companies have continued to clash over Unix ownership claims, as Novell has deepened its investment in Linux, most recently with its purchase of No. 2 Linux seller SuSE Linux.

"SCO takes this action today, given Novell's recent and repeated announcements regarding their claimed ownership of the Unix and UnixWare copyrights," SCO lawyer Mark Heise said in a statement. "SCO has received many questions about Novell's actions from potential customers, investors and the press. Although SCO owns the Unix and UnixWare copyrights, Novell's efforts to claim ownership of these copyrights has forced this action."

A Novell spokesman declined to comment on the lawsuit but said the company stands behind its earlier statements regarding its Unix position. Novell has said the U.S. Copyright Office granted the company copyright registrations for 11 versions of System V Unix, giving Novell a substantial ownership position.

Novell bought Unix from AT&T in the 1980s and sold at least some rights to a predecessor of SCO in 1995. Novell claims that it retained some rights to Unix and related works; SCO claims that it bought all rights to Unix and that any Unix-related copyrights granted to Novell are therefore invalid.

The lawsuit accuses Novell of "slander of title" for continuing to suggest that it has a stake in Unix. "Novell, with full knowledge of SCO's exclusive ownership of copyrights related to Unix and UnixWare, has embarked on a malicious campaign to damage SCO's ability to protect its valuable copyrights in Unix and UnixWare," according to the claim. "Novell's wrongful claims of copyrights and ownership in Unix and UnixWare (have caused), and continue to cause, irreparable harm to SCO."

The suit seeks unspecified punitive damages and injunctions that would transfer to SCO any Unix-related copyrights obtained by Novell and bar Novell from "representing in any forum that it has any ownership interest whatsoever in Unix and UnixWare copyrights."

The lawsuit comes on the eve of the LinuxWorld trade show in New York, where Novell is set to play a prominent role following its acquisitions of SuSE and desktop Linux specialist Ximian.

SCO lobbed a similar surprise before the August version of LinuxWord in San Francisco, when the company revealed steep licensing prices for those who wish to use Linux with SCO's blessing.

Lawyer Jefferson Scher, a specialist in intellectual property issues at Palo Alto, Calif.-based law firm Carr & Ferrell, said the latest lawsuit may quickly be added to SCO's case against IBM.

"There is a chance the judge will say, 'Why are you here? Take this to the other court,'" Scher said. "I think it's logical for the court that's hearing the copyright case to decide if the plaintiff owns the copyright. This appears more like an attempt to get a restraining order."

Whatever court hears the case against Novell, the judge is likely to have a tough time sorting out the intent of Novell's 1995 transaction.

"Contracts like this are difficult enough to parse out at the time they're singed, let alone many years after," Scher said.

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