I remember seeing it! my friend was into C64 and then the Amiga. He was a musician/coder and wrote music (and drivers) for games on the above (still does, GB Advance now), he had a copy of it some 10 years back and showed me.
It is possible that it was simply an OS emulator (which is what I thnk) or even a program that simply looked and worked idetial to GEM - iether way I did see it.
I did ask him the other day if he could remember what it was called but he could not.
Not long after it was circulating there was an Amiga "emulator" for the ST (I think on some demo or cover disk). It was simply an app that looked the same and had no functionality apart from a few menus and double clickable icons.
