[zengargoyle]

I'm talking about AmigaOS. Bits and pieces were based on https://en.wikipedia.org/wiki/TRIPOS and the kernel itself had a lot of UNIXy sort of features. In the late 1980s if your work job is sitting in front of a Sun workstation you bought an Amiga for home instead of a Mac or DOS machine. I would dial my Amiga into work before going to work and remote shell in (rlogin/rsh/rcp) and just shuffle things back an forth without effort. One could do CS homework both on the Amiga and on the SunOS systems just by linking to a different library. I never even had a C compiler on my AMIGA, didn't need one. I can't imagine writing some code on UNIX and that trivially making it run on a Mac or DOS machine. People even build stub UNIX libraries for AmigaOS that faked the user/group/permissions and other bits of the UNIX experience. It was just a pleasant experience for those late 80s compared to the alternatives.

AMIX is a whole different can of worms, they did that much later and I'd expect it was like porting between HP/UX, AIX, BSD etc. Probably pretty easy by then.