In a letter on the Novell website from chief executive officer and president Jack Messman, the company challenged SCO's assertion that it owned the copyrights and patents to Unix System V.
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Novell, which had earlier acquired the Unix systems business of AT&T, broke up and sold its Unix properties in 1994 and 1995. One of those deals was with the former Santa Cruz Operation, which was bought by Caldera International and later became The SCO Group.
In his letter, Messman said the purchase agreement entered into between Novell and SCO in 1995 did not transfer the System V rights to SCO.
"To Novell's knowledge, the 1995 agreement governing SCO's purchase of Unix from Novell does not convey to SCO the associated copyrights," Messman wrote.
"We believe it unlikely that SCO can demonstrate that it has any ownership interest whatsoever in those copyrights. Apparently you share this view, since over the last few months you have repeatedly asked Novell to transfer the copyrights to SCO, requests that Novell has rejected."
Messman's letter also asked SCO to prove immediately its assertion that certain Unix System V code has been copied into Linux.
"SCO claims it has specific evidence supporting its allegations against the Linux community," Messman's letter said. "It is time to substantiate that claim, or recant the sweeping and unsupported allegation made in your letter. Absent such action, it will be apparent to all that SCO's true intent is to sow fear, uncertainty and doubt about Linux in order to extort payments from Linux distributors and users."
In a reply to Messman's letter, SCO stated, "SCO owns the contract rights to the Unix operating system. SCO has the contractual right to prevent improper donations of Unix code, methods or concepts into Linux by any Unix vendor.
"SCO's lawsuit against IBM does not involve patents or copyrights. SCO's complaint specifically alleges breach of contract, and SCO intends to protect and enforce all of the contracts that the company has with more than 6,000 licensees. We formed SCOsource in January 2003 to enforce our Unix rights and we intend to aggressively continue in this successful path of operation."
The growing battle came to a head in March when SCO sued IBM for $1bn, alleging that the company misappropriated trade secrets related to SCO's Unix products to benefit IBM's Linux strategy.
As for SCOsource, it was created to enforce what SCO claimed was its position as the majority owner of Unix intellectual property.
In another startling move, SCO sent out a letter two weeks ago to nearly 1,500 global companies which use Linux in their businesses, warning them that they should seek legal advice because their use of Linux could leave them liable for damages over SCO's pending intellectual property claims.
Messman's letter included an open letter to SCO CEO and president Darl McBride, outlining Novell's announcement last month that it is moving its product line to Linux and pointing out Novell's commitment to Linux and the open-source development community.
Messman said Novell was one of the companies that received SCO's warning letter, which "compels a response from Novell".
"In particular, the letter leaves certain critical questions unanswered," Messman wrote.
"What specific code was copied from Unix System V? Where can we find this code in Linux? Who copied this code? Why does this alleged copying infringe SCO's intellectual property? By failing to address these important questions, SCO has failed to put us on meaningful notice of any allegedly infringing Linux code, and thus has withheld from us the ability - and removed any corresponding obligation - to address your allegation."
Messman wrote, "SCO continues to say that it owns the Unix System V patents, yet it must know that it does not. A simple review of US Patent Office records reveals that Novell owns those patents."
Graham Bird, a spokesman for The Open Group, which has owned the trademark for Unix on behalf of the Unix industry since Novell transferred it in 1994, said SCO is wrong to assert that it owns Unix. "What they own is some source code and technology" for UnixWare, said Bird. "That's not the same thing as owning Unix.
"If you're an uneducated observer of this, it would be very easy to say that SCO owns Unix, which is not the case," Bird said.
Bruce Perens, a key figure in the free software and open-source communities and a critic of SCO's recent actions, lauded Novell's move.
"Novell has answered the call of the open-source community," Perens said. "Based on recent announcements to support Linux with NetWare services and now this revelation ... Novell has just won the hearts and minds of developers and corporations alike."
Dan Kusnetzky, an analyst at market research firm IDC, said the Novell letter widens the battleground. "This is a set of intriguing developments that stands to only help one company, and it's none of the companies that are participating now."
The likely beneficiary would be Microsoft because the legal squabbles could hurt the Linux market and turn businesses against even thinking about additional Unix deployments, Kusnetzky said.
Todd Weiss writes for Computerworld