This is the complete source code for winquake, glquake, quakeworld, and glquakeworld.

The projects have been tested with visual C++ 6.0, but masm is also required to build the assembly language files. It is possible to change a #define and build with only C code, but the software rendering versions lose almost half its speed. The OpenGL versions will not be effected very much. The gas2masm tool was created to allow us to use the same source for the dos, linux, and windows versions, but I don't really recommend anyone mess with the asm code.

The original dos version of Quake should also be buildable from these sources, but we didn't bother trying.

The code is all licensed under the terms of the GPL (gnu public license). You should read the entire license, but the gist of it is that you can do anything you want with the code, including sell your new version. The catch is that if you distribute new binary versions, you are required to make the entire source code available rce code available for free to everyone.

However, word from John Carmack is that they are holding on to the 'game source' code for Quake3 for a while since they are still making changes to that part of the code base. Here's the .plan update

The Q3 game source code is getting pushed back a bit because we had to do some rearranging in the current codebase to facilitate the release, and we don't want to release in-progress code before the official binary point release.
We still have a Christmas present for the coders, though: http://www.idsoftware.com/q1source/ Happy holidays!

After you grab all your cool new toys, the Quake3 Editing board is there for the taking.