SCO Group has announced that IBM no longer has the right to use or distribute the Dynix/ptx operating system it acquired when it bought Sequent Computer in 1999.
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IBM's rights were terminated because it refused to remove almost 170,000 lines of Dynix/ptx source code from the Linux kernel.
The move is the latest in a series of claims and counterclaims between SCO and IBM, dating back to March, when SCO sued IBM, claiming it had, inappropriately, contributed source code, to which SCO has the rights, to the Linux operating system.
SCO is already seeking more than $3bn in damages from IBM, and has already revoked IBM's licence to distribute its AIX operating system, which is based on Unix source code controlled by SCO.
IBM has insisted 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 GNU General Public Licence, which 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," said SCO spokesman Blake Stowell, adding that these contributions violated a clause in IBM's contract which states that work derived from SCO's System V Unix code must remain part of System V Unix.
On 16 June, SCO gave IBM 60 days to remove the 148 files of Dynix/ptx Unix code it contributed to Linux, a deadline which expired on Tuesday.
IBM, which uses Dynix/ptx as the operating system for its Numa-Q line of servers, declined to comment on this story.
Robert McMillan writes for IDG News Service