[timetopay]

Unix is both a family of operating systems and also a trademark. The name is overloaded - "Unix" is more than one thing at the same time. In addition, the trademark is "UNIX" and the operating system family is "Unix"

MacOS is both UNIX and also not Unix at the same time.

If the trademark holders decided to UNIX certify my cat, which is well within their legal right to do so, would that make her UNIX?

[greggsy]

Unlike macOS, your cat does not, and will not, meet the industry-accepted standard that describes unix as we know it today.

https://www.opengroup.org/openbrand/register/xym0.htm

[bigyabai]

Like macOS, my cat does not qualify for the UNIX standard out-of-the-box and I'm far too lazy to configure my cat for an OS standard that's 25 years obsolete.

[shiomiru]

> as we know it today

An important nuance you seem to be missing is that SUSv3 is equivalent to "IEEE Std 1003.1-2001" (that is, POSIX 2001).

In practice, I've had to work around more POSIX compatibility issues in macOS than in all other actively developed (Free) Unix-likes, combined.

[remix2000]

Mayhaps not with a `cat(1)` alone, but really they just need to expand their menagerie now.

[remix2000]

Or perhaps they just won't certify your cat just as Apple won't start making Windows PCs…?