I read that the NeXT, let's call it, "adventure", is the reason Apple went with a Linux distribution as basis for their new OS and thus, we're all using OSX now?
NeXT is the reason Apple went with a UNIX-type OS that evolved into OS X, yes.
Linux is also a UNIX-type OS, but is not an ancestor of OS X.
Linux is so popular now that it's easy to identify it with UNIX but historically it's only one of several implementations that work in roughly similar ways.
Other replies are telling you which code OS X was actually descended from.
It's in the name.
(I'd just like to interject, etc.)
Stallman was a prodigious programmer and wrote GCC (GNU C), a debugger and Emacs. He also created the GPL and founded the Free Software Foundation (from which the "open source" movement split off).
GNU was most of an OS by 1990 but didn't have a proper kernel (which was intended to be the ambitious Hurd).
In an unrelated move, Linus Torvalds used Stallman's tools to write a mini-OS and released it under Stallman's license in 1991. It naturally got incorporated into what some people (including Stallman) then called GNU/Linux. It was, in code terms, roughly 97% GNU and 3% Linux.
The naming is arguable because Linux was never a GNU or FSF development. However, Stallman's GPL allowed Linux operating system packagers (eg Debian) to use things that had been developed by or adapted for GNU.
Otherwise, Stallman told me he wouldn't have bothered with GNU if he'd known that BSD Unix was going to be available as free software. Unfortunately, FreeBSD wasn't released until 1993.
The only real reason that a Linux distribution hasn't been UNIX-certified is because RedHat and IBM found there was very little marketing value in calling it UNIX, that is, Linux is a stronger brand.
And I suspect the only reason MacOS is UNIX-certified is because they advertised it as "UNIX" and were sued by The Open Group, who owns the trademark. [1]
[1] https://www.cnet.com/news/apple-in-court-dispute-over-unix/
It's based on Red Hat. It has been officially certified as UNIX by The Open Group.
And that means all the basic tools and system calls one expects on a true UNIX machine are present in OSX.
”MkLinux started as a project sponsored by Apple Computer and OSF Research Institute, to get "Linux on Mach" ported to the Macintosh computer and for Apple to explore alternative kernel technologies on the Mac platform. At the time, there was no officially sponsored PowerPC port of Linux, and none specifically for Macintosh hardware”
> Around 2005, Jobs faced a crucial decision. Should he give the task of developing the device’s software to the team that built the iPod, which wanted to build a Linux-based system? Or should he entrust the project to the engineers who had revitalized the software foundation of the Macintosh? In other words, should he shrink the Mac, which would be an epic feat of engineering, or enlarge the iPod? [1]
When this article first came out, I made the assumption that this statement meant iPod OS was Linux-based---also feel like I heard that somewhere else---but I have not found any sources to confirm this. Anyone else know?
[1]: https://www.bloomberg.com/news/articles/2011-10-12/scott-for...
http://www.sfgate.com/default/article/Little-known-startup-w...