Carmack didn't write any of the code that Zenimax claimed was derived from what he'd written at id. He hasn't done any work on the PC side at all.
That's one of many messed up things about this case. When Zenimax sued Oculus they assumed Carmack had been working as part of the existing Oculus team, but he'd actually started up an entirely separate project, working with Samsung on mobile VR, it just hadn't been announced yet.
That caused problems for Zenimax, and the list of misappropriated trade secrets shrank to seven software features that the expert witness was certain had been copied, whereas it was originally "all software and all hardware except the display and lenses."
Another witness with actual expertise in VR quickly established that none of the seven features were even trade secrets.
That's one of many messed up things about this case. When Zenimax sued Oculus they assumed Carmack had been working as part of the existing Oculus team, but he'd actually started up an entirely separate project, working with Samsung on mobile VR, it just hadn't been announced yet.
That caused problems for Zenimax, and the list of misappropriated trade secrets shrank to seven software features that the expert witness was certain had been copied, whereas it was originally "all software and all hardware except the display and lenses."
Another witness with actual expertise in VR quickly established that none of the seven features were even trade secrets.