Varis, uqm is faithfully ported from the original (opened) 3DO sources for Star Control 2. You can even choose which version you want to see, if there are differences in the 3DO and PC versions...

The occasional jerkiness is definitely because it's too 'heavy', but it remains to be seen how much is "acceptable overhead" and how much is just weird code (resulting from the original code being from another platform) -- I beleive there hasn't been much interest in optimizing since it works fine on even older PCs.