TCMU2009: Okay, thanks. I'll try that. Wasn't the Dark Engine source code found in some modders basement last year? I remember reading about it in PC Gamer. I thought it would be released to the public so people could do all sorts of stuff with it.
Yes, but the problem is that Eidos has yet to authorise the source being released to the public. It probably doesn't help that the source wasn't just the Thief games but also System Shock 2, which Eidos doesn't have the rights to (EA holds at least some rights to it).
There's still the possibility of someone at Eidos sorting it out one day (maybe for some good PR in the lead-up to Thief 4?) but at this point it looks like the best approach would be to wait for some group to make a reverse engineered engine remake.