When Apple introduced the first shipping version of OS X, in the form of its OS X Server product (back in March 1999, according to Wikipedia <https://en.wikipedia.org/wiki/Mac_OS_X_Server_1.0>), it did a naughty thing. It advertised it as a “UNIX” product. But “UNIX” is a trademark belonging to The Open Group, and can only be used with permission. Apple didn’t have that permission. The trademark owners responded by filing a lawsuit for US$200 million. Apple could have responded in one of two ways: * License the “UNIX” trademark. This would require a lot of fixes to the OS X code in order to pass the compliance tests. * Acquire The Open Group, and thereby gain the rights to use the “UNIX” trademark however they wished. The company decided to go for the first option. Here <https://www.quora.com/What-goes-into-making-an-OS-to-be-Unix-compliant-certified/answer/Terry-Lambert> is a first-hand account from Terry Lambert, the technical lead charged with making OS X fit to be called “UNIX”. The project required a lot of fixes, not just to Apple’s code, but to a bunch of code from the various open-source projects that Apple had copied. I don’t think anything Apple has done since then has contributed so much back to the open-source world. And then there is this article from early last year <https://www.osnews.com/story/141633/apples-macos-unix-certification-is-a-lie/>, provocatively entitled “Apple’s macOS UNIX certification is a lie”. Because it seems The Open Group’s criteria for granting a “UNIX” trademark licence are, shall we say, somewhat lax. First of all, they don’t require that you certify against the latest version of the spec; an old version, last updated over 20 years ago, like the one Apple used, is just fine. And then, they allow you to handwave away failures of particular tests if you offer suitable excuses -- something Apple has done quite liberally. Does the “UNIX” trademark still mean anything any more? My feeling is that Linux compatibility matters more than any legalistic “UNIX” conformance, and the actions of both Apple and Microsoft nowadays indicate that they understand that quite well.