I think this is fantastic news, since I taught myself how to program by typing games, written in BASIC, into my Timex-Sinclair and tweaking them to see what happens. Games today are far too large to do anything like that, so it's great that id provides a way for people to learn game programming from the real thing.
Earlier today, I compiled the code from the provided Visual Studio project file, and ran it with no problems. You have to have an original copy of the game for all the models and levels, since only the source code was released, but it is super easy to run. Just go the directory with the newly built binary and run this from the command line:
./quake3.exe +set fs_cdpath "C:\Program Files\Quake III Arena"
(assuming you installed the retail game in "C:\Program Files\Quake III Arena").