It’s not confusing at all, if it’s a derivative of ATT Unix it’s referred to as “Unix”. Why you thought that excluded OSX in your post above no one will ever know, and why you want to blur the lines between Unix and foreign clones like Linux doesn’t make any sense either. I’d recommend just keeping quiet on the matter to you finally figure it out, should that day ever come.
So what is a derivative of AT&T UNIX? Is it the codebase that makes it a derivative? BSD was rewritten to remove almost all AT&T code so that only a small fraction of one percent of the files had any AT&T (actually USL) copyright as of 14 years ago. On top of that, OS X doesn't even use the BSD kernel, but Mach. It contains the BSD userland and many utilities, but remember, BSD started as Berkely-written utilities for AT&T UNIX.
There is barely any, if any, codebase lineage to AT&T from OS X, yet somehow we refer to it as UNIX.
And if you sell your "Unix" without it being certified UNIX then you may be sued for trademark infringement even if it is an AT&T derivative. The people who own the name consider "UNIX" to be conforming to the standards, nothing to do with lineage. Or don't you believe they have the right to enforce their trademark?
I’d recommend just keeping quiet on the matter to you finally figure it out, should that day ever come.
No thanks. I'll stay and keep injecting facts into your fantasies.