Don't get me wrong I like how Tremulous is opensource. It just seems strange to me that someone would discourage other people from using their code when they used a fairly liberal licence like the GPL.
Because when you take the code, then make it incompatible with the original product, that is a fork. Forking is something frowned upon because it splits the fanbase and potential developers in two, ending up getting nothing done for the original product, and the fork going nowhere. Why would it go nowhere? Because the fans of the original product get bored and leave, while the fork gets none of the users of the old product, thereby leaving it in a state of useless development for nobody. Forks are sometimes beneficial(take a look at XFree86/Xorg), but in this case it's of no use to anyone to take the code then break compatibility, when you could be sending patches in to the original product, furthering it to 1.2 status. I believe TremFusion will go the way of Cedega, having some nice features but eventually being phased out by the original product(Wine).
The XreaL renderer is nice but there has yet to be a discovered way to port it in its current state to ioQ3 without breaking compatibility with 1.1 servers. The XreaL renderer depends on a new BSP version, which means all maps would have to be recompiled, not to mention converted to Doom3 format first. Think this is easy? Think again. I've gone through this grueling process. It is not fun or worthwhile.
About my screenshot: It is old as hell and was taken when HDR was new, and before the new BSP format(which meant no HDR lightgrid!) resulting in what looks like shit compared to now. The current HDR is so much better than it was back then.
I agree that getting a new renderer would be a 2.0 thing, not 1.2. 1.2 is getting closer and closer every day. If we keep adding new things to bugfix, 1.2 will never get done. A new renderer is not for a mere point release.