Apple bough a port of UniSoft SYSVr2 to the Apple platoform and dubbed it A/UX. Version 2 onward were technically significant as ToolBox and Finder had been ported to Unix and allowed MacOS apps to run on top of Unix. They didn't offer process virtualization so they could all crash eachother out.

The A/UX Toolbox PDFs cover a lot of interesting technical details for the curious: http://bitsavers.org/pdf/apple/mac/a_ux/aux_2.0/030-0787-A_A...

"/mac/sys — This directory contains the system folders for startup and login. The System file provided with Release 2.0 of A/UX is almost identical in functionality to the System file provided with Release 6.0.5 of the Macintosh system software."

Additionally I always thought the Gestalt Manager was a System 7 thing and was surprised to learn it was introduced along with system 6.0.4 and A/UX so applications could tell if they were running on it: https://developer.apple.com/library/archive/documentation/ma...

Still, since you didn't need to run MacOS apps much, it wasn't really a problem. MacOS couldn't crash the Unix or X subsystems, or anything (else) on them, and nothing else could crash MacOS.

Why would I try harder for something that _might_ be interesting? That's just bad writing.

If I can’t tell what something’s about from the first couple paragraphs or a quick skim, I’ll tune it out. I have plenty of other content to read.

I chose to introduce it slowly setting where it came from. I wasn't aiming to write an encyclopedia entry. Otherwise it'd be a one liner.

Can't please them all.