That needs to be revised for VL7. But i'm not sure we have VL7 packages in the repos for this, although the slack 13.0 and 13.1 builds work fine... I use this to access my server + virtual machines remotely.
Here is a link to the packageshttp://connie.slackware.com/~alien/slackbuilds/freenx/pkg/13.0/
Download all the .tgz files and do installpkg on them.
Find or build a netcat package
Find or build an xdialog package
The most common problem after installation is a locked "nx" account. To diagnose any session problems, run `tail -f /var/log/messages` while trying to connect from a remote host (note: connecting from the local machine will not work).
If you see something saying user nx is not allowed, see herehttp://alien.slackbook.org/dokuwiki/doku.php?id=slackware:nx