This question has really got me thinking about the old days! I thought that it was looking into Debian Linux when trying to repurpose some old IBM PS/2 machines at work, because there were rumors of patchsets for the Linux kernel to support the MicroChannel Architecture bus and ESDI drives. But now I remember that it was actually GeekGadgets, a Unix environment for Amiga based around the ixemul.library. That's where I first read the GPL, and admired its legal Jiu-Jitsu of using copyright laws to ensure freedom.
I've never been a Windows user on my own machines as a result. I just went from Amiga, to FreeBSD, to Ubuntu.