When Apple built MacOS... for Solaris and HP-UX. In 1994.

Back in 1994, Apple released the Macintosh Application Environment for UNIX. And it was kind of amazing.

Read the full article (with links to documentation and screenshots) at The Lunduke Journal:
https://lunduke.locals.com/post/4812552/remember-when-apple-built-a-mac-os-running-on-top-of-solaris-and-hp-ux-seriously-it-happened