IBM has filed a 100-page motion with a US district court in an attempt to have some of the claims made against it by The SCO Group dismissed.
SCO's case against IBM alleges that Big Blue broke its Unix contract with SCO by putting SCO's code into the open source Linux operating system.
But IBM's motion for partial summary judgment states: "Although SCO for months perpetuated the illusion that it had evidence that IBM took confidential source code from Unix System V and 'dumped' it into Linux, it has become clear that SCO has no such evidence."
The motion goes on to contend that SCO's claim now rests on the assertion that contributing IBM's own code from IBM's two Unix-based operating systems, AIX and Dynix, breached the contract.
In a series of assertions IBM denied putting any Unix System V code into Linux, and said SCO had produced no evidence that it had.
The company also claimed that it is entitled to put code into Linux from AIX and Dynix as long as it does not come from Unix System V, and that SCO was wrong to suggest otherwise.
Even if had put Unix code into Linux, argued IBM, Novell had retained rights over Unix covering this when it passed Unix to SCO, but had waived them on behalf of SCO.
IBM asserted that SCO had subsequently also waived these rights by selling or making available to its customers the code it said IBM should not have revealed (by also providing Linux).
Novell's claim to have retained the Unix copyright has been contested by SCO and is the subject of a separate case.
The hearing on IBM and SCO's counter-motions is likely to take place on 15 September.
IBM and SCO had not commented at the time of going to press.
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