At my University I heard things like "Linux is derived Unix, BSD variants are something else entirely". I think education people are confused in general about this topic.
That's hilarious. It sounds like you know, but for anyone who doesn't, it's actually the opposite. BSD variants are derived from Unix--that's where the BSD comes from, it was the Berkley Software Distribution of Unix tools, that later implemented the rest of Unix so universities could use the same software without having to worry about licensing from Bell Labs.
Linux is something else entirely, a student's project to make a MINIX compatible kernel, usually packaged with the GNU operating system, which like BSD aimed to be Unix compatible, but notably is not Unix (It's right there in the name: GNU's Not Unix).
The operating system interface that Unix, BSD and Linux share is called POSIX. The term POSIX is not widely known, so people sometimes make up for it by using "Linux" in-place because it is the most popular implementation.
This explains people who argue that Android is not Linux, despite it featuring a Linux kernel and self-identifying as so: They are intending to say that Android is not POSIX.
We need to make POSIX (as concept/word) more popular.
Especially to package writers that assume bash is available everywhere, hope that bin/sh is the same as bin/ksh...sed -i... not on unices, grep missing a ton of options....
It's never going to happen. POSIX has been around for 4 decades now. The longer something is not popular, the lower its chances to ever become popular.
