The Message-Editor is a 'Mr. Pip Thingy'.
To be find at his old website :
http://mrpip.orcon.net.nz/nw54/nwscripts.html
The How-to for the smilies pop-up is to be find here:
http://www.rattarium.net/N54/n54_smilies1.html
Im not too sure if the editor-code is working along with the Network54 wysiwyg editor (really i never use this feature), but if it works with your forum you'll prbably don't need the N54 editor any more.
If you like to see if you can it working I'd suggest to try out on a forum-dummy (test-forum), this way you would destroy anything in your 'running' forum.
Or - you may wait a few days (weeks, months?) for Network54' new release of the forum software, which will include a new editor, I guess.
good luck.. ed