I know a number of people have been using the nx/freenx packages available from the centos-extras repo. Now, EPEL recently started distributing NX packages. When you run 'yum update' with epel enabled, it will replace CentOS' nx as seen here:
http://pastebin.centos.org/8101/
Have any of you tried EPEL's version? If so, can you share your findings?
The open-source edition of NX (version 3.5.x) is virtually static because there would not be updates from NoMachine. I don't know if EPEL made any changes/additions to what CentOS offers.
Akemi