space exploration/trading game?

[Prometheus]

and Apparently the original Elite is out on the Nes, and works really well, best of all, the Ian Bell (one of the creators) hosts the rom on his website, so it's legal

Yep - and if my memory serves me correctly, he has most (or all? I'm unsure on this point) of the other versions of Elite available, too. Clearly one of the gems of the legal emulation list (even though it's not my cup of tea, personally).