I have sold tons of Embosstracks...the reason they are coming available is due to a lack of replacement parts, so purchasing expensive software to make a potentially temporary plotter run might not be too wise, but if you can get software cheep, a lot of people loved those units.
1-Some had limited success with MacImprint, some versions were better then others, don't expect any support from anyone on this, its just that almost nobody runs or remembers how to run it.
2-Omega or Graphix Advantage on a PC, probably the best solution, just check first if you are buying an older version that it will work on your windows platform. Buy it from somebody who knows what the latest version their dongle is upgraded to, just because it says say 1.56 on the dongle, does not mean it is so...it could be upgraded some.
3-Other programs...Signlab and Flexi, both have run it, you might have to set it up as an HPGL device. This sometimes means that the plotter will have some issues recognizing the limits along the width of the vinyl and if you send a job that is too wide, it will still go, but could not finish the sides and will not panel correctly.
4-Buy something a bit newer and use it on HPs trade up program for an L25500 printer...I think they give you up to $5000 for the thing! lol. (Actually I think this deal is over)
Hope that helps!
Craig