But GEM ran on 2 different platforms: DOS PCs, and on the Atari ST. The Atari version was not affected by Apple's lawsuit and delivered a very slick interface.
Ahem! Sorry, those screenies don't show GEM as it looked at the times.
That looks like something from https://en.wikipedia.org/wiki/MiNT which although started early after, wasn't that common and/or usable. It got a boost in development much later only, IIRC.
What can be seen there is a work of love/passion, from not that much people, running in an emulator, which enables configurations which were either very expensive, rare, or didn't even ever exist.
What I am saying is much simpler: that DR didn't deliver a Mac-like GEM on the PC for the excellent reason that Apple sued them to stop them doing it. That's why PC GEM got crippled, and ended up as just a file manager/app launcher in the form of ViewMax.
(It is also worth nothing that Caldera subsidiary Lineo made GEM GPL around the turn of the century, and since then, PC GEM regained all the features Apple made DR remove and more, including Bézier curve support and things.)
All I am saying is that Atari GEM wasn't crippled, was a popular and well-loved GUI that people are still using and working on even today.
What can be seen there is a work of love/passion, from not that much people, running in an emulator, which enables configurations which were either very expensive, rare, or didn't even ever exist.