Oops, slow response, sorry. Must see if I can subscribe for notifications to the entire community.
Geoff Crammond is in the Special Thanks section, but I deliberately tried to avoid using his name or The Sentinel brand to promote the game, as that would be trademark violation - but I've acknowledged the debt in interviews. Game designs can't be copyrighted, fortunately - otherwise we wouldn't have the concept of "genres" and id would be the only company allowed to make an FPS :)