wolfsrain: Maybe because the "new" Steam version is the old Dungeon Lords MMXII renamed?!
The game had a troubled development cycle. It was always a bug mess. The first version was updated to 1.4, but it never solved any of the problems that the game had. In the end they released Dungeon Lords Collector's Edition, a version of the game that at least was playable.
Jowood in their hunger for money decided to make a new game named DL: The Orb and The Oracle. Money running out and the new trend being remaster/remake/HD versions, Jowood decides to remake the original game under the name Dungeon Lords MMXII. Same problems as the original game with some extra added. The game got a bad rep on Steam and not only. Nordic getting the IP from Jowood for pennies, they've retired the old MMXII version and brought in a renamed game.
I'd say GOG made the right call. If any version has a place on GOG, that would be the DL: CE (v1.5). That's the one that at least works in some capacity (it's still bugged, but not as bad as the other versions).
Actually the Developers claim newly released version is enhanced beyond MMXII or the CE, now i cant verify this but thats what the Devs are saying on the Steam fourms.