29 September 2003 IBM has filed an amended counter-suit against SCO Group, expanding its claims of copyright infringement by SCO and highlighting a 1996 agreement that could invalidate SCO’s termination of IBM’s Unix licence with SCO.

“These counterclaims arise from SCO’s efforts wrongly to assert proprietary rights over important, widely-used technology and to impeded the use of that technology by the open source community,” claims IBM in its filing.

It goes on: “SCO has misused, and is misusing, its purported rights to the Unix operating system… to threaten destruction of the competing operating systems known as AIX, Dynix and Linux and to extract windfall profits for its unjust enrichment.”

IBM claims that SCO has breached a number IBM’s copyrights on technology it has donated or developed for Linux, by continuing to distribute its own version of Linux after making its proprietary claims over the open source operating system.

By making its claims over Linux, yet continuing to distribute its own version, SCO has invalidated the licence under which IBM released the technology in the first place, claims the company.

“By distributing Linux products under the GPL [general public license] , SCO agreed, among other things, not to assert — indeed, it is prohibited from asserting — certain proprietary rights over any programs distributed by SCO under the terms of the GPL,” states the filing.

It adds: “SCO also agreed not to restrict further distribution of any programs distributed by SCO under the terms of the GPL.”

IBM has also brandished an October 1996 agreement with Novell, the owner of AT&T’s Unix intellectual property between 1992 and 1996, and Santa Cruz Operation (SCO), one of SCO Group’s predecessor companies that bought the intellectual property from Novell.

This agreement gave IBM the “irrevocable, fully paid-up, perpetual right to exercise all of its rights” under the original 1985 licensing agreement with AT&T over the Unix intellectual property that forms the basis for IBM’s AIX Unix.