SCO alleges (Paragraph 57): \ufffdWhen SCO acquired the UNIX assets from Novell in 1995, it acquired rights in and to all (1) underlying, original UNIX software code developed by AT&T Bell Laboratories.\ufffd

SCO neglects to mention that those rights had been substantially impaired before its acquisition of the ancestral Bell Labs source code. There was a legal action in 1992-1993, in which Unix Systems Laboratories and Novell (SCO's predecessors in interest) sued various parties including the University of California at Berkeley and Berkeley Systems Design, Inc. for alleged copyright infringement, trade secret disclosures, and trademark violations with regard to the release of the open-source 4.4BSD operating system[10].

The suit was settled after AT&T's request for an injunction blocking distribution of BSD was denied in terms that made it clear the judge thought BSD not unlikely to win its defense. The University of California then threatened to countersue over license violations by AT&T and USL. It seems that from as far back as before 1985, the historical Bell Labs codebase had been incorporating large amounts of software from the BSD sources. The University's cause of action lay in the fact that AT&T, USL and Novell had routinely violated the terms of the BSD license by removing license attributions and copyrights.

The exact terms of final settlement, and much of the judicial record, were sealed at Novell's insistence. The key provisions are, however, described in Twenty Years of Berkeley Unix: From AT&T-Owned to Freely Redistributable, [McKusick99]. Only three files out of eighteen thousand in the distribution were found to be the licit property of Novell and removed. The rest were ruled to be freely redistributable, and continue to form the basis of the open-source BSD distributions today.

That is, ten years ago at a time when Linux was in its infancy, the courts already found the contributions of other parties to what is now UnixWare to be so great, and Novell's proprietary entitlement in the code so small, that Novell's lawyers had to settle for a minor, face-saving gesture from the University of California or walk away with nothing at all.

This history is well-known in the open-source community, and helps explain why SCO's claim that ownership of the historical Bell Labs code gives it substantial rights over other Unixes such as AIX is regarded among old Unix hands with near-universal disdain. Some of the court documents, including the 1993 ruling are now available on the web [11].

[...]

Since IBM's AIX is well known to contain large portions of Berkeley code (towards which IBM has by all accounts met its license obligations) SCO's theory is at best extremely dubious. In other words, to prove its right to relief SCO will need to show that whatever code IBM gave to the open-source community was neither legally obtained by both IBM and SCO from a common source nor independently developed.

[... Much later ...]

Furthermore, SCO is barred by the terms of the GNU General Public License from making copyright or patent-infringement claims on any technology shipped in conjunction with the Linux kernel that SCO/Caldera itself has been selling for the last eight years. Therefore, SCO may accuse IBM of misappropriating SCO-owned software to improve the Linux kernel only if that software does not actually ship with the Linux kernel it is alleged to be improving!

Finally, SCO is barred from making trade-secret claims on the contents of the Linux kernel, not merely by the fact that the kernel source is generally available, but by the fact that SCO has made the sources of its Linux kernel available for download from SCO's own website! [23].