The current version of XFree86 is 4.2.0 as of this writing.
It can be downloaded as source or binaries. It is generally recommended
to download the binaries these days. See
http://www.XFree86.org for
the lastest official information on installation of XFree86.
Later in this document, I describe only the very basic procedure
for compiling and installing from the source.
XFree86 source code comes in three files:
X420src-1.tgz
X420src-2.tgz
X420src-3.tgz
doctools-1.3.tgz
utils.tgz
Doctools is the DocBook SGML package used by XFree86 to prepare the X documentation.
Utils contains the source for the "extract" program, which is a modified GNU tar with
gzip support. Extract is only important if you are installing a binary distribution
of XFree86 on top of your existing XFree86 to upgrade it. Extract unlinks old existing
files that are being extracted/updated instead of skipping them. Extract comes with the
binary distributions so utils.tgz is only important for making your own binary
distribution.
You can download XFree86 from its ftp site:
ftp://ftp.xfree86.org/
XFree86 includes
GLX,
the OpenGL X interface functions.
Each window system has to provide the platform-specific interfaces
between OpenGL and the window system for mapping a GL rendering
context to a window system widget. Recent versions of XFree86, like
version 4.2.0, now also include libGLU and the OpenGL manual pages.
Free eBook: 
