Linux is not unix, by the way. Besides the obvious things (linux is just a kernel), the unix specification has many mandates in terms of API (for compatibility

Linux is not unix, by the way. Besides the obvious things (linux is just a kernel), the unix specification has many mandates in terms of API (for compatibility), in terms of behaviour and even in terms of commands and utilities (a specification of a vi editor is also in the unix specification iirc). So yeah as long ad Microsoft doesn’t try and get anything certified as unix, they’re fine I guess (but I’m not a lawyer). Worth noting: mac os is unix (every release gets certified iirc).