Gatekeeper (gk) is a H323 GateKeeper based on the OpenH323 project.
It is released with the GPL (GNU Public Licence)

A H323 Gatekeeper manages multiple H323 clients on a network
and provides a nice user name to IP mapping.

As it follows the H323 standard, it is compatible with H323
client programs inclding voxilla, OhPhone, OpenPhone and MS NetMeeting.

It makes use of PWLib and the OpenH323 stack from Equivalence Ltd Pty

It's currently maintained by Jan Willamowius <jan@willamowius.de>
WWW: http://www.willamowius.de/openh323gk.html

Also see
http://www.openh323.org