Does GOG.com version of Ultima 7 use DOSBox or Exult, the fan reimplentation of the game engine, to run?

Also, has anything been done about the copy protection questions when trying to leave the town you arrive to at the begining (Trinsic?).

Most likely DOSBox.

Probably, but would like a confirmation from someone who has tried the GOG version. ;-)

I'll get top men on it. *Top men.*

Fixed ;-)

It's Trinsic, yes. As for the copy protection, the questions are probably still there (since they weren't taken out of VI), but since the download includes the manual with the necessary information it's more of an annoyance than a show-stopper. (The original code for Ultima VII was sadly lost years ago, so branching around the copy protection -- as some other GOG games have done -- is likely a nontrivial prospect.)

It's good in that the games are fully playable and winnable in their original DOS versions; Exult, although it's approximately a 98%-complete implementation of the engine, still exhibits some show-stopping bugs that didn't exist in pure DOS.

It's bad in that Exult does offer several helpful enhancements, including improved inventory management in The Black Gate (importing the paper-doll system from Serpent Isle) and support for higher-resolution screens.

In the end, it's more a matter of personal taste and what you consider more important.

I can attest to the fact that Ultima 7 (gog version) uses DOSBox by default. However, you can install Exult if you so wish. I did so, and it runs like a charm.

Brilliant.

Can you switch between playing with Dosbox or Exult (do they use the same savegames?) or doesn't it make sense anyway since the showstopping bugs in Exult would ruin the whole thing anyway?

From the Exult FAQ:

2.6. Do save games from the original work in Exult?

Save games that were made with the original Ultima 7 or U7Run don't work with Exult. You have to start a new game when you begin playing with Exult. Sorry!

So I guess the answer there would be no, saves aren't cross-compatible... bummer.

Well, I finished Ultima 7 with Exult a couple of years ago and I must say that I haven't encountered any bugs which would cause my game to become corrupted or prevented me from completing the main quest. Perhaps I was the lucky one, but Exult is as stable as you can get. Considering the tricks Origin had to use to make Ultima 7 work, I'd be more worried about the native DOS environment.

I've read that showstopping bugs encountered using Exult can be fixed by reverting to an earlier saved game.

the GOG version is using DOSBox and it runs just like the original did back on the old AT 386 for which it was optimized. The GOG experience is almost always going to be a step back in time rather than a customization. It is probably possible to use Exult with it, however, since all the files are there. I prefer the original myself, however, as that's the way I remember it.