@gamingonlinux I tried GemRB a couple of years ago but got the impression that it still wasn't a good experience, but still a curious experiment.
The worst part was how unstable it was, causing frequent crashes more often than the original game engines. This would be one of the most desirable traits, improved stability and crash management like you get with OpenMW (The Morrowind open source engine project).
Has it gotten better? I can't seem to find any recent gameplay or reviews of it.