MARK 5.0 is now the release version of MARK. You can grab it from Gary's site, or from this mirror at
http://www.phidot.org/software/mark/download/
For those of you working with Vista (no, 'working' and 'Vista' are not entirely contradictory terms, although I have no desire to work with Vista myself), you might want to consult the MARK FAQ
http://www.phidot.org/forum/viewtopic.php?t=9
for some of the things you *might* have to deal with to get MARK to 'play nice' with Vista.