Basically it’s a GNU screen with X server and suspend/resume.
It’s all there:
add-apt-repository ppa:freenx-team/ppa
wajig update
wajig install neatx-server
To use suspend u need to have a window manager set. I like ratpoison as it’s lightweight, all apps are fullscreen by default and there’s no Alt-Tab shortcut, so whenever there will be an NX client for the N900, ratpoison makes switching windows easy (plus: alt-tab conflicts with my default window manager).