I never quite understood what the point of this was beyond marketing. Linux is also not listed probably because no one ever paid to have it listed

Apparently it was for legal reasons. Apple was sued by the Open Group for describing Mac OS X as Unix® so they decided it was cheaper to bring it up to spec rather than to fight the lawsuit.

https://retrocomputing.stackexchange.com/questions/27095/why...

https://www.quora.com/What-goes-into-making-an-OS-to-be-Unix...

It is specific Linux distributions that would be Unix-certified. Huawei had one; not sure if it has ever been on this page.

Enterpise espeically banking need standard and certification for reliability thats why , also certain Linux distro had certified before from China based on RHEL.

This is UNIX 03 certified OS with OSS alternatives from I gathered on internet :

- Apple OS X 10.7 - Apple macOS 26 , provide OSS Darwin 9 - Darwin 26

- Oracle Solaris 10 / 11 , provide OSS OpenSolais , then Illumos

- EulerOS 2.0 , based on RedHat Enterprise Linux / RHEL 7 and 8

- Inspur K-UX 2.0 , based on RedHat Enterprise Linux / RHEL 5

- Inspur K-UX 3.0 , based on RedHat Enterprise Linux / RHEL 7

Linux can’t be listed, because Linux is not an operating system. It’s just a kernel. Unix specifies a whole operating system, which includes things like libc, cat, sh etc.

At best a distro could be certified. But that certification would not automatically extend to other distros.

Enterprise. Checklists.

It was a legal problem, and an interesting story: https://www.quora.com/What-goes-into-making-an-OS-to-be-Unix...

And Gnu’s Not UNIX.