Pantheon desktop from elementaryOS.
You can use it on their distro (Ubuntu based with lots of curated apps) or on its own (you can still get access to their curated apps, just not in the store)
EDIT: Sorry, I misunderstood. You want classic Mac. I’d say get Xfce4 and theme it yourself then.
- PlatiPlus for window manager theme
- Platinum Gtk2 Theme
- Platinum9 for the Icons
Here’s an example: https://www.reddit.com/r/unixporn/comments/4l9tlp/xfce_another_nine_based_os_9_based_theme/
Rust and Haskell (I think Haskell counts)