linux is an open source re-implementation of the unix kernel.

If you want to read all about it, go to http://www.groklaw.net.

However, the bottom line is: SCO lost. Very badly.

Yes, Unix was/is a fine operating system. But when Linux came along and developed an entirely new open-source operating system that was quite obviously inspired by what Unix had originally done ... it did not actually steal from Unix. Neither did the GNU = "Gnu's Not Unix" project. It turns out that you can build a car with four wheels, a windshield and a steering-wheel and not pay royalties to Oldsmobile.

how i understand the story is that in the 1960's at&t bell labs developed an operating system named multics (multi because it was a multi-user os and ticks were a method of counting the execution time of programs).

they had a relationship with a few universities like mit and university-cal-berkeley (bsd = berekley software distribution) and for student research and recruitment they would donate part of the sourcecode. it was a limited part of the operating system that supported single user processing (uni meaning one). after many iterations of senior design upgrades the donated source code (and free labor) of unix surpassed the functionality of the corporate backed multics.

sco - santa clara operating systems was founded by graduates of university-cal-berkeley.

ibm-aix is based on at&t system-v unix and apple-osx is based on bsdi kernel.

linux is based on a brand new kernel that is posix compliant (very similar to unix) but does not share any of the code base.

I have to disagree here. Linux shares no code or development history at all with Unix. The kernel was developed from scratch as a substitute for Unix for a person who could not afford Unix licensing. The GNU runtime is, of course, more complicated.
I'd say calling Linux Unix confuses matters. Depending on how you measure it Linux us now the dominant OS and to call it Unix lumps it together with those which are less succesful and thise which are commercial.
You can refer to a Dyson as a Hoover if you wish* but I find it strange to do so.

*I realise by market share the analogy doesn't work, but I think the names give the general idea I'm trying to convey.

Neither does "official" UNIX, MacOS X.

The Mach kernel on which it is based does not have any AT&T UNIX code. Nor do FreeBSD or NetBSD, which became code contributors to NeXSTEP.

If being code-related to academic research operating systems branched off of BSD UNIX makes an OS worthy of the name UNIX in your mind, then throw a party, because pretty much everything we use can at least tenuously make a claim to that mantle. Remember, while the AT&T code ran alongside and integrated with original BSD code for a very long time, and, in the various System V releases, AT&T UNIX ingested a lot of BSD code into itself, in the long run the flow of source was only one way; By the time you get to 4.3BSD-Lite, 386BSD, FreeBSD, NetBSD, and all their little children, there is no AT&T UNIX code included. None. (That's one reason why FreeBSD can't be called "UNIX" any more than Linux can, legally.) All of those projects knew that the copyright on that AT&T code made it impossible to keep around, and so there were concerted efforts to ditch all of it.

You could argue that, even once that AT&T code was purged, the common development history of BSD UNIX and AT&T UNIX creates a special worthiness of descendant BSD incarnations to be called UNIX more than GNU or Linux.

So ... before Linux came around, do you think that the GNU userland wasn't built and tested with BSD UNIX kernels? And ... you think the Linux kernel wasn't built and tested against the very same GNU userland? (And probably various BSD/GNU hybrids as well?) So, really, all of this software shares a development history, even if there were more than a few Chinese walls up at the time.

None of this stuff was developed in a vacuum. Conceptually, their modern day incarnations are all direct descendants of the original UNIX.

Of all the "UNIX or UNIX-like" operating systems in use today, the only one which to my knowledge may contain some code directly derived from the original UNIX is Solaris, and perhaps by extension some related open source projects like Illumos and OpenIndiana. (I'm pretty sure that any residual AT&T code has been replaced in all of these projects, though, including Oracle's.)

All of this makes it ridiculous, in my opinion, to go around making the "code descendant" argument. MacOS ain't no code descendant. You pay the Open Group a bunch of money, submit to some testing, and your OS can be called "UNIX(TM)."

TL;DR - None of today's OSes were developed in a vacuum, and (almost) none of them have any UNIX code in them. They're all equally conceptual UNIX descendants, so get over yourself already. Any flotsam OS can have the word UNIX purchased and hung on it now.

By that definition Windows 8 is Unix.
Either Wikipedia and the books I've read are lying or BSDSo, despite not being certified as with the Single UNIX Specification they are still classed as UNIX in certain discussions because they share a code base.
Linux is neither certified nor shares a code base. It's "UNIX LIKE" of course.

Actually, that's POSIX compliant https://en.wikipedia.org/wiki/POSIX, and as it says at the top there
As previous posts point out, legally only OSes that have been certified can use the word (trademark) UNIX, and they (OS manufacturers) stick to that.

As also pointed out, the origins of BSD lay in AT&T, but all of that code was eventually purged, see the court case quoted above.

Linux is a Unix work-alike, but was written from scratch, not derived (code level) from any Unix.

Novell owns Unix copyrights https://en.wikipedia.org/wiki/SCO_v._Novell.

No, they don't share a code-base. They do share a common specification, e.g. POSIX. And, yes, even Windows has some POSIX-compatible commands.

Even GNU is a de facto standard, and you can download Windows implementations of a great many of these commands. They work fine.

Think about it ... if a layer of software exists, such that "the program you want to run" actually runs, neither you nor your program has any particular interest or reason for dumpster-diving down to "the guts of the thing." The program runs, just like you want it to. That's what cross-platform is really all about.

Yes, the Linux system supports POSIX system-calls which are the "common ground between it and Unix" from a program's point of view ... and it has a similar filesystem structure most of the time ... and it recognizes the chmod nomenclature even though it doesn't have to implement file-security that way ... and so on and on. But there's just as much divergence between the systems, too. For instance, there is no /proc filesystem in a Unix box. There is no PAM (iirc ...).

What SCO failed to understand is that there is no intellectual-property protection merely for what something "looks like" or "acts like." (And, that it does not pay to try to hold IBM and the rest of the industry hostage after they very-graciously offered to buy you out so that you'd go away and shut up.)

the same way that ford crown victoria, lincoln town car, mercury grand marquis are all ford vehicles because they are built from the same base (same platform, car frame, factory). chevy caprice classic, though very similar, is independently built and shares no parts with the fords to the best of my knowledge.

The question of what is or isn't UNIX is up to money.

As far as I know, neither Linux nor any of the BSD systems are UNIX.

Only by paying for a certification test (and passing) will anything be allowed to use the UNIX trademark.

Yeah ... a more apt comparison would be the 1960s A/C Cobra.

We're essentially arguing whether or not modern replicas should be called "Cobras." BSD and Linux would both equally qualify as "replicas," maybe with additions like power steering, fatter tires, and tighter, more modern suspensions.

They'd certainly rank under a hypothetical car built from actual 1960s Cobra parts in competition for the name, or a still-working original which has been modified for competition, but in the case of this analogy, no such car exists for comparison. Rather, we only have other cars which are also modern, tweaked replicas, the builders of which have payed a royalty for use of authentic-looking badging.

Does not having payed for the nameplate make one incorrect in referring to their replica as a Cobra?

... whereas use of the Linux® trademark is still without fees.

... and I daresay that it, in today's pragmatic "our only collective purpose here is to get done" times, is by far the more significant. (Just sayin' ...)

Unix was the baby of AT&T geniuses like Dennis Ritchie. It is intimately bound up with the development of the C programing language. Whilst it was originally intended not to be multi-user (hence the name, as opposed to the abandoned Multics) it quickly became so.

It was a personal project. I guess that, even today, the big companies have research labs just doing stuff --- and its lack or "corporateness" is marked. Compare the language of the manuals, for starters: does it mention "Bell Labs" every second word? No.

The release to education was to do with the restrictions on monopoly. Bell Labs was not allowed to actually sell Unix. It was not a marketing move, in the way that today's software giant[s] will try to lock students into their OS. Bell labs had nothing to sell: they could not sell it, and used it internally. It was, for them, a happy accident, that a generation of students, after college, wanted to use Unix.

This is my rough, very incomplete, 3.40am bit of the story. The history is in the history books, or, more easily, the internet. The history of Unix is a really good story: check it out, and read to your kids at bed time. Once upon a time... It might even be part of why I fell in love with it!

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You can only use it if you are using the Linux kernel, as that is all it covers.

UNIX. on the other hand, covers the kernel, and the utilities. You can only pass the qualifications by having all features of UNIX, and the registration fees. Linux, BSD, Windows, and even MacOS X cannot pass even the basics. The best that Linux BSD, and MacOS X can claim is UNIX LIKE.

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foodown, a lawyer would disagree with you, as would all of the distro and BSD variants apparently. Not one of them dares to call their products UNIX.

I'm sure why anyone cares at this stage. There is no shame in just being Linux.