This is a patched version of xdm to use an external greeter program.
The default external greeter is  /usr/local/bin/xlogin, however it
can be changed in /usr/X11R6/lib/X11/xdm/xdm-config.cpp using the
DisplayManager*egp resource.

For more information check:

  http://tr.ml.org/~tom/software/xdm/

