multi universes on one computer

Not possible. cant run the same program twice. one universe per computer. sorry to say but under the assumption that most dj's have usually way less than a dmx universe and if you have more than one dmx universe you would be more likely to pick up a multiple universe controller such as a SD2 or SD3 or even compu live.
Sincerely,

Gotta keep in mind that MyDMX is a lower-end type product. By that, I don't mean junk, but rather, not a super blown out "every feature you can think of" package. Still, for the price, it packs a LOT and makes MyDMX a great value for the money.

The way I see it, I have a real world application where I would need to have access to more than one universe, but not at the same time. For example, my regular lights, then the lighting rig at a specific venue, which they could email me their room and universe.

I do know of some lighting consoles with multiple universes. The main reason they used different universes was mainly for quicker and logical control over groupings and changes on the fly. Of course, other applications may vary.

I would agree that most people are not even fully populating the Universe they have. Most tours I have seen are in the same situation as well: still have channels left over should they need them.