[KallDrexx]

Carmack wasn't a freelancer working under Zenimax on an hourly basis. He was a full time employee working on the same industry in games, and as ex-CTO of id (and knowing what we know of Carmack's talents and what he's done before) he was most likely doing a lot more research and prototyping work in his capacity at Zenimax. Therefore it's a lot less obvious what he has ownership of vs what Zenimax has ownership of.