the AT&T codebase didn't have native TCP/IP networking support until Sun's contributions were folded into SysV.
After being slammed on the stolen-code accusation, SCOX claimed a broken business deal over Project Monterey (IBM & Santa Cruz co-developing UNIX for IA-64/Itanium aka "Itanic" for how quickly it sank in the market); Santa Cruz sold out to Caldera and IBM used the change-of-control clause to walk, since they hadn't been consulted at the time. The code IBM took back was stuff they'd brought in from AIX & Sequent anyway so nothing to claim there.
SCOX had their heads handed to them in the Novell slander-of-title case when the original lawyers confirmed from their own notes at the time that no, copyrights never transferred to Santa Cruz so SCOX never had them either, so no grounds to sue over infringement. Novell immediately mooted any copyright charges against IBM.
The IBM suit and the other accessory cases such as Red Hat's were about to be judged, presumably against SCOX, when they filed Ch. 11 to preserve what cash they had. They spun off unXis n/k/a Xinuos as a software operation, and kept the never-ending lawsuit expecting to get something, somehow, from IBM.
Xinuos went from a rent-an-office in the Bay Area to an incubator park in USVI, moved the underlying kernel to BSD, and this spring launched their own version of the suit after claiming at the spinoff they had no interest in litigation. Guess supporting an OS associated with frivolous lawsuits against customers wasn't as profitable as they thought. This settlement will likely scuttle their own case once it comes up, or at least one can hope so.
XINUOS DELENDA EST!!