Looks like the NX guys are folding shop to be pay only software and FreeNX doesn't have a client for Windows and other OS's

http://arstechnica.com/civis/viewtopic.php?f=16&t=1227519

Looks like yet another endless FOSS forking contest. NX > FreeNX > X2Go. Hopefully X2Go sticks. Looks good so far, it has the NX back-end but they have their own clients, Windows too.