IBM has escalated its legal counterattack on the SCO Group by filing new claims alleging that SCO has infringed IBM's copyright.
IBM and SCO have been disputing each other's intellectual property claims surrounding the Linux and Unix operating systems since March, when the company sued IBM, claiming that IBM's contributions to the Linux operating system violated IBM's Unix contract.
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In August, IBM filed a counter-lawsuit against SCO, maintaining that SCO had violated not only the GPL (GNU General Public License) software licence that governs Linux, but also a number of IBM software patents.
The counter lawsuit asserted that SCO's rights to distributed Linux had been terminated.
IBM added the charge of copyright infringement to its lawsuit.
The amendment also asks the court to rule on whether SCO has the right to seek a $699-per processor licensing fee it is now demanding of Linux users.
"One of the counterclaims is that SCO infringed IBM's copyrights by, among other things, copying and distributing IBM contributions to Linux without permission after SCO's rights under the GPL were terminated due to their breach," said Bob Samson, IBM's vice-president of systems sales.
SCO has not sold the SCO Linux software in question since 12 May, but the company continues to distribute it via the internet to honour existing support contracts, said SCO spokesman Blake Stowell.
Stowell disputed the idea that SCO could no longer distribute Linux. "We're the copyright holder for the core Unix operating system. If we want to charge someone a licensing fee for using our copyrighted software that's gone into Linux, then we have that prerogative," he said.
"If we want to continue to distribute Linux to our existing customers, we can do that because we own the copyrights on that Unix software."
Robert McMillan writes for IDG News Service