Desktop Classic System is an operating system based on Debian and a customized version of the MATE Desktop Environment that hearkens back to, but is not a direct copy of, the classic Mac OS. DCS seeks to provide and sometimes even improve upon the conceptual simplicity offered by the old Macintosh.
↫ Desktop Classic System website
I’m usually not particularly interested in reporting on random Linux distributions, but any one of them that defaults to a proper spatial file manager is one that I will highlight. I’m not entirely sure if this is just a supported feature of MATE’s file manager, or something more custom – there are some patches to Caja here, as mentioned – but spatial file managers are a dying breed and that’s a shame. They’re hard to implement and even harder to get right, which is probably why few people take on the challenge.
Other than that, DCS isn’t particularly revolutionary or special, but I’d love for more Linux distributions to look back at what we’ve lost, and see if we can bring those things back.

Looks like gnome 1 on top of nautilus (the best version imho).
Needs a global menu.
Doesn’t look too much like classic Mac OS. And besides that, I passionately hate spacial file managers (the first thing I do on a new Haiku install is switch Tracker to non-spacial mode). If I want the Mac OS classic feeling from time to time I start up my QEMU vm with 9.2 installed.
If this works, it might be the only way I’d use MATE.
Looks really great. I couldn’t get it to boot for now (might be EFI only)