Apple already had a unix-based Mac OS for five years by the time Jurassic Park came out, A/UX. My first computer job was at a nascent ISP around this time and most of the servers (mail, www, accounting) were Quadras running A/UX. One IIfx with several massive (for the time) hard drives for Usenet. It was basically the System 7 (Mac) UI bolted on top of System V unix.
"Everybody" had Unix systems back in the day. People forget that there was a time when it was seen as critical to have a Unix offering to be taken seriously in certain markets.
On the "low end", besides Apple's A/UX, Microsoft had Xenix and Commodore had Amiga Unix.
also MachTen, Tenon's UNIX on MacOS. it ran as a process on top of MacOS, not in place of (as A/UX did). i never got my hands on A/UX but ran MachTen for a while in grad school (i was too poor to own an SGI). this was before LinuxPPC and MkLinux/PPC were around, and before UN*X ports to mac68ks were working.
