- Fire up X11.app (It's located in /Applications/Utilities/X11.app)
- On Mac box: go to X11 preferences and enable "Allow connections from network clients" (Make sure it looks like below)
- Restart X11.app
- Open a terminal in X11 and do: xhost +
- ssh to your linux box and do: export DISPLAY=IP_OF_MAC_BOX:0.0
Bingo! On the linux box, you can now run any X app, say xterm and the X window will pop up on your Mac box.