It would be pretty comical to do so, just to muddy the already muddy term. But it has very little practical utility. I don't think any regulatory body require

It would be pretty comical to do so, just to muddy the already muddy term. But it has very little practical utility. I don't think any regulatory body requires a "real" UNIX these days -- sure, some products require a particular OS like AIX but I haven't heard of a spec/customer/vendor demanding "UNIX". Most clueful people would talk in terms of POSIX and {POSIX, UNIX, Linux}-like to describe the desire for portable software APIs or whatever. Upon more thought, maybe all caps UNIX should refer to the legacy AT&T system. In the modern lexicon, Unix is mainly two things: a command environment (i.e. a shell with UNIX-like built ins and pipes) and a philosophy (shell, simple short commands, pipes, hierarchical file system, less is more etc). This use still has great meaning to me and I wish more people would spend the time to learn the culture, reading books like those by author Peter H. Salus. Using those definitions, it should still be common to talk about "Unix shell scripting" or thinking about software design in a "Unix environment", even if that were to execute entirely on Linux in practice.