From a trademarking stance, the only 'True" unixes are those that pay to get certified by Single UNIX specification. Of those, two are commercial Linux distribu

From a trademarking stance, the only 'True" unixes are those that pay to get certified by Single UNIX specification. Of those, two are commercial Linux distributions, and the rest (including macOS) are proprietary unix operating systems https://en.wikipedia.org/wiki/Single_UNIX_Specification#Currently_registered_UNIX_systems https://en.wikipedia.org/wiki/Single_UNIX_Specification#Curr...