Gede: It may be a licensing thing.
snowkatt: or lack of interest from EA
But EA does not have to do anything other than give their OK.
The way I see it, extending the distribution to Linux implies paying EA more than GOG thinks is worth it in a new licensing deal. So you may call it a lack of interest from EA by not making it easier to happen, I can see that. But we could also say that GOG has not enough interest in striking that new deal using the same logic. Maybe they are both unreasonable.
In the meantime, check out
for playing Ultima VII or [url=http://nuvie.sourceforge.net/]Nuvie for playing Ultima VI on Linux. Your package manager may carry them. Other similar projects for other Ultimas can be found on
Ultima Codex. On the forums you may find some help on figuring out the best configuration for your own DOSbox.