To make a Unix system available as a server for GAP you must (1) install
GAP3d on /usr/local/lib/courier, (2) run xnscourierd from /etc/rc.local
or wherever, (3) run (once) the program ../examples/ch/registerhost
to register this host in the clearinghouse.

We have tested GAP3d with XDE NSChat, with Star, and with Interlisp CHAT.
It seems to work adequately.
There is also an untested GAP version2 server available as GAP2d.