"We are restating that SCO owns the Unix operating system along with all the contracts, claims and copyrights associated with Unix," said SCO chief executive officer Darl McBride.
"We also reassert that portions of System V code are found in Linux," he added, as well as portions of resulting derivative code.
The battle of who actually has Unix property rights surfaced three weeks ago, when SCO warned all commercial Linux users that they could be using its code illegally and recommended that they seek legal advice to help them decide what to do about their use of Linux.
That was followed last week by Novell's call for SCO to put up or shut up over its allegations. In a letter on its website from Novell CEO and president Jack Messman, the company lashed out by challenging SCO's assertion that it owns the copyrights and patents to Unix System V.
Novell, which had previously 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 SCO.
In March, SCO sued IBM for $1bn, alleging that the company misappropriated trade secrets related to SCO's Unix products to benefit IBM's Linux strategy.
SCO's McBride said last week that some industry analysts had accepted an offer to view some allegedly misappropriated code and that they have come away agreeing with some of SCO's assertions.
"These initial reviewers appear to be coming to the same conclusions as we have, namely that SCO's Unix source code has made its way into Linux," he said.
McBride claimed that two documents found by SCO confirmed the company's claims. The documents are an "Asset Purchase Agreement" between Novell and SCO from September 1995, and an amendment that followed in October1996.
Novell has acknowledged that the amendment "appears to support SCO's claim that ownership of certain copyrights for Unix did transfer to SCO in 1996".
However, Novell added, "The amendment does not address ownership of patents, however, which clearly remain with Novell." It also asked SCO to address its "still unsubstantiated claims against the Linux community".
Gartner analyst George Weiss said SCO's documents could bolster the company's claims. "They have documents that to me look very legitimate," he said.
Weiss had met SCO to review the Unix claims, but he refused to sign a nondisclosure agreement, so he was not permitted to view some of the contested code. SCO "gave me enough information that there could be something there [to the claims]", said Weiss. "They're not doing something frivolous."
In a bid to clarify its claims against commercial users of Linux, McBride said he would try every option before resorting to litigation. "We plan to work out the issues with customers in a short, straightforward and amicable way," he insisted.
SCO has been receiving feedback from commercial users and is developing licensing programs to resolve any issues, which will be unveiled in July, McBride said.
McBride added that SCO expected to resolve issues with commercial Linux suppliers, such as Red Hat and SuSE Linux, "in ways short of litigation".
Todd Weiss writes for Computerworld
This was first published in June 2003