Its the doorway at the very end of that clip - it causes an exception and we don't handle it yet (I suspect Linux etc silently ignore it)Do you mean the door where the cutscene "took you some time, marine" starts?
Good job, dhewg! I cloned the git repo today and I was suprised that you didn't remove the cd key check. I don't know if you didn't do it because you just didn't think of it or because you take the same stance as the ioquake3 project. If that's the case, come on, most of us bought the game years ago in a shop or a few months ago on Steam after it was open-sourced (or both like me). This will only annoy potential testers/players and it won't bother the pirates at all.
At first I thought copying the doomkey file from my Steam installation on Windows partition to /usr/local/games/doom3/base/ would work, but it doesn't. I had to define ID_ENFORCE_KEY 0 to disable the cd key check.