X11 and XFree86 were initially developed on Unix-based systems. Usually Unix systems provide a rich number of tools and utilities to get certain things done. Under OS/2, these tools are not installed, but ports are available which are sometimes functionally equivalent to Unix utilities with the same name, but also differ sometimes in a subtle way. This guide will give you hints if you intend to rebuild the system from scratch under OS/2.
Please also read README.OS2 for end-user information, and set at least the environment variables described there.
At the current time, the most recent version available is XFree86-3.3. This is a full and unrestricted version which comes with complete source code. 3.3 is an intermediate version which was released because the last beta version (3.2A) was about to expire and the new 4.0 version was not completely finished in time. 3.3 is the last ``classical'' version which has separate Xservers for different video cards.
If you want to join the XFree86 developer team, e.g. to add support for certain hardware, please send a request to BOD@XFree86.org. Please think about such a step carefully before, though, since much work is involved. Please use the XFree86-3.3 source code as a test example how to compile the system. The ability to manage that is a basic requirement for becoming a developer.