IBM is increasingly confident in the ongoing copyright battle over Linux source code.

In an amended counterclaim to SCO's lawsuit that was filed in Friday, IBM asked the US District Court for Utah to enter a declaratory judgement in its favour.

It had not infringed on SCO's copyright or breached its contractual obligations with SCO, the filing claimed. And SCO, at one time a Linux vendor, cannot impose restrictions on the software that it previously distributed under Linux's open-source software licence.

By seeking a declaratory judgment, which a judge could issue as soon as the discovery process is over and before the case goes to trial, IBM is indicating it has conducted an internal analysis of SCO's claims and has found them to be without merit, claimed Jeff Norman, an intellectual property partner with Kirkland Ellis.

"It just means that they didn't find any smoking gun. If they had found something really bad, they probably would have gone to SCO and talked settlement," Norman said.

It should be emphasised that a declaratory judgment is different from a dismissal, which is a motion that the case can not stand because of some legal defect in the filing. For example, Novell is seeking a "dismissal" of its case from SCO.

It would be typical in a case like this for IBM to undergo an internal investigation to determine whether or not any of SCO's claims were true, he said. Such an investigation would involve interviewing and reviewing e-mail and code contributions from IBM's Linux programmers.

IBM has over 7,500 employees involved in various aspects of its Linux efforts, including more than 600 developers who work in the company's Linux Technology Center.

Jeffrey Neuberger, a partner with Brown Raysman Millstein Felder & Steiner, agreed that the filing appears to show growing confidence on the part of IBM. "They're saying to the judge: 'We don't know what SCO is talking about; there is no infringement'," he said. "They must feel very comfortable that there's no infringement."

Because IBM's filing seeks the broad judgement that IBM has not infringed on "any valid or enforceable copyright owned by SCO", a declaratory judgement in its favour would prevent SCO from bringing up new copyright claims later in the trial, and would have a devastating impact on SCO's case, Neuberger said.

"If the judge comes out and says there is no copyright infringement, then essentially there is nothing else to fight over. It would be the knockout blow to SCO's case," he said.

Representatives from IBM and SCO declined to comment on Friday's court filing.

SCO sued IBM in March 2003 claiming that it had violated SCO's Unix licence, which was originally granted by AT&T but later transferred to SCO, and that it had illegally contributed source code to Linux. In February this year, SCO amended its complaint to include charges that IBM had violated its Unix copyrights. SCO is seeking $5 billion in damages.

However, whichever way it falls, it is unlikely to be in the near future - the discovery process alone can last for years, Neuberger said.