There is Atom these days which is OS and similar to ST.
Mind you, Atom takes longer to start than Visual Studio.
VS Code is open source and starts as fast as notepad.exe. Also, I think it has more features than atom.
Which UNIX isn't proprietary?
Note UNIX, not UNIX like.
All of the BSDs.
Which of them is certified as such?
Who really cares about whether something is "certified" UNIX? Certification is not some seal of quality. "Unix" is commonly understood to denote "functional" unix systems as well for lack of a more convenient term.
That os what the UNIX-like expression is for.
OS X would have been the only one certified. Even then I wouldn't call it a BSD per-se.
Oh, didn't realize you meant only certified Unices. I'll be on my way...