Hey all, sorry I didn't respond to all of your comments. The reason there is just a .dll is because you download the mod Action Quake 2 and then you replace the .dll with the one in the zip. I didn't have permission to distribute all of the art assets, so that was the easiest solution.
If there is any interest in this I might recompile it for whatever the newest quake 2 engine release that is popular.
For a long while I didn't have access to my machine with the source code, but I recently fixed the machine and now have it again.