Remote Mac X11 Programming
Mac OS X now provides support for Unix X11 Windows programming! Panther (OS X 10.3) ships with support for the X Windows GUI and includes the XTools IDE and X11 SDK on the Developer CD. So you have all the tools for compiling and running X Windows GUI programs on the Mac. X11 applications should be portable to Unix, Linux and even Windows systems running X11.
More interesting is the power of running X11 applications over a network. By its inherent nature, all X11 applications are divided into a client and a server portion. This inherent division in X11 applications provides built-in support for network remote access. X11 forwarding allows your application to run on a remote host machine while displaying the X11 Window on a local machine!
This page provides the information that you need to build a "Hello World" X11 application and then communicate with the application over a network.
Have fun.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20040208015717450