If you'd like a ready to compile distribution of QuakeWorld that has this HOWTO's procedures performed on it already, then you can download it at:
http://www.comptechnews.com/~reaster/index.html#games
Otherwise ...
It seems that the glqwcl.glx binary available at least at www.quakeworld.net in the package qwcl-2.30-glibc-i386-unknown-linux2.0.tar.gz is not compiled properly since on startup, it looks for libglide2x.so.
QuakeWorld clients come in several flavors:
glqwcl (3dfx only?)
glqwcl.glx (MesaGL/XFree4)
qwcl (svgalib)
qwcl.xl1 (x11/svgalib)
This HOWTO is only concerned with getting the glqwcl.glx working with XFree86 4.x with GLX.
This HOWTO assumes you have a working OpenGL libGL/libglx installation!
If you happen to have an Nvidia card and are interested in a complete HOWTO for installing the Nvidia drivers and an assortment of OpenGL libraries (GLU, glut, Qt, OpenGL man pages), then see the NVIDIA-OpenGL-Configuration_miniHOWTO at:
http://www.linuxdoc.org/HOWTO/mini/Nvidia-OpenGL-Configuration-mini-HOWTO/