the nxplayer is the preview player for version 4 of the NX technology: looks still incompatible with the previous 3 version (needs a server of version 4 too, but should be fixed in future releases).
neverthless, I prepared
a testing slackbuild.
if you are interested in the previous (STABLE) one, have a look at slackbuilds.org: you will need
nx and
freenx on the server that exports the display and
nxclient on the client that you want to use.
here you can read how to use the slackbuilds.