You can freely download an NX client for Mac OS X from
NoMachine's website. However this client is not fully compatible with the
FreeNX package (which is actually based on the same sources as NoMachine's NX server).

You can successfully connect to a FreeNX server, but the keypresses are not transferred correctly (some garbage comes out on the FreeNX server instead of what you really pressed). I've found a workaround however it is a bit cumbersome:
- start clean, so neither the NX Client, nor X11 should be running
- start the NX Client, set up a session and start the connection (the NX Client will start X11)
- after a successful connection suspend the session (press the "x" in the top left corner of the window), but keep X11 running (this is important!)
- now reconnect to the suspended session and this time the keys will work correctly
This works both with the U.S. and with the Hungarian keyboard layout.
Comments
Happens with offical NX Sever too!
Thanks for the pointer - I'll just keep my sessions running and reconnect to them until someone from NoMachine sorts the client out...
but testdrive works!