Stop asking sensible questions
This ancient case used to be covered thoroughly on Groklaw - until personal threats against PJ made that too dangerous. The case starts with Caldera/TSG/... doing a thorough job of delaying making any kind of clear accusation followed by demands for an enormous amount of discovery materials then more delays to read through the discovery materials. Eventually Darl had no choice but to make a verifiable/falsifiable complaint. I cannot remember that far back to what the complaint was but I do remember the refutation:
IBM wrote some design documentation for some features.
Some IBM staff used the documentation to code the features into AIX.
Some other IBM staff used the documentation to code the features into Linux.
Darl claimed to own Unix (rubbish - if it belonged to anyone that would have been Novell at the time)
Darl claimed that anything added to IBM's AIX was his because of his fake claim to Unix.
Darl claimed ownership of the completely different code in Linux because of the fake claim to the code that was not in Unix.
Darl was not a completely clueless idiot. He convinced David Boies of Boies Schiller Flexner to fight this through the courts and all the appeals up to SCOTUS for a percentage of the profits. Boies quickly worked out be had been scammed and dumped all the work on a junior colleague. BSF also sent bills for expenses back to TSG. TSG payed those bills by collecting Novell's royalties (as TSG were contracted to do) and not sending any of the money to Novell (contract required sending 100% and Novell would send commission back). Just before an expensive ruling against TSG could land, TSG declared bankruptcy. Effectively, Darl gets replaced by a court appointed trustee with a far better understanding of nuisance litigation. The trustee promptly spent all of Novell's revenue on legal firms to ensure that TSG's creditors never got any money and dragged this rubbish on for years at the expense of IBM and BSF.
There never was any valid claim. TSG had no standing to sue (that would have been Novell and they instructed TSG to end the litigation). With the help of the bankruptcy court this has effectively become Tax Payers vs IBM and even IBM does not have the funding to win that one no matter how daft the accusations.
[IBM were not the only defendant. There were other claims of ownership to code in the Linux kernel including code created by Caldera and contributed by them to the Linux Kernel with a GPL license. The code was removed shortly after this became an issue - no one was using it anyway.]