[dekhn]

you're right, Mac OS X is a derivative of BSD but it also has significant Mach tech (like the linker).

I've used freebsd for years and I still find Mac OS to be the least useful UNIX.

[smhenderson]

Ironic it's one of the few (only?) popular, widely deployed ones left that gets to sport the fact it's a certified Unix OS - https://www.opengroup.org/openbrand/register/

[dekhn]

Sort of. I see this a different way. Many years ago, Linux replaced UNIX as the "standard UNIX", and certification become irrelevant.

Further, unless I'm missing an important technical detail, Linux could, with some effort, pass the certification process.