IBM no longer has the right to use or distribute the Dynix/ptx operating system it acquired in its 1999 purchase of Sequent Computer, The SCO Group said.
IBM's rights were terminated because the computer maker refused to order almost 170,000 lines of Dynix/ptx source code removed from the Linux kernel, SCO said.
The move is the latest in a series of claims and counterclaims between SCO and Big Blue, dating back to March when SCO sued IBM, claiming the computer giant had inappropriately contributed source code, to which SCO has the rights, to the Linux operating system. SCO is already seeking more than $US3 billion in damages from IBM, and has already revoked IBM's license to distribute its AIX operating system, that is based on Unix source code controlled by SCO.
IBM has said it has done nothing wrong, and last week countersued SCO, claiming that SCO had wrongfully asserted rights over Linux. IBM also accused SCO of violating the GPL (GNU General Public License) software license that governs Linux as well as a number of IBM's software patents.
IBM did not have the right to contribute the Dynix/ptx source code to Linux, SCO said.
"Shortly after IBM acquired Sequent, IBM contributed both NUMA (non uniform memory access) and RCU (read copy update) code from Dynix to Linux," SCO spokesman, Blake Stowell, said.
These contributions violated a clause in IBM's contract that stated that work derived from SCO's System V Unix code must remain part of System V Unix, he said.
On June 16, SCO gave IBM 60 days to remove the 148 files of Dynix/ptx Unix code it contributed to Linux, a deadline that expired on Tuesday, according to Stowell.
IBM, which uses Dynix/ptx as the operating system for its NUMA-Q line of servers, declined to comment on this story.