A few years ago Microsoft claimed 40% of the server market. I assume they wouldn't have been deliberately underestimating!

The one place you can check OS use is with web servers, since most will reveal their OS. The domination of Linux over other Unixes is impressive.

Silicon Graphics dropped Irix, HP's HPUX is largely for legacy hardware, Solaris is Linux-compatible in its libraries and has a small user-base, the original Unix is tied to SCO, BSD is a very small-scale affair, OSX may be certified but is only compatible without graphics. Really the only flourishing Unixes are Linux and AIX.

I certainly don't agree that BSD are small scale. One way of measuring success might be numbers of servers but there are other ways, e.g. volumes of data served. In this area FreeBSD in particular is doing very nicely, e.g. here is a quote from the freebsd-stable mailing list earlier this year where Netflix about their shift to FreeBSD for content delivery,

Consider also that a variety of server products are based on FreeBSD, e.g. Citrix Netscalers, Juniper Networks Junos network operating system (used in their routers, switches and security devices), various NetApp devices (NetApp's products and solutions are currently powering 96% of FORTUNE 100), Nokia's firewall operating system, Blue Coat's ProxySG WAN acceleration appliance (Blue Coat provides products to more than 15,000 customers worldwide, including 88% of the Fortune® Global 500). And these are just a few examples. Consider also the impact FreeBSD has on mainstream consumer products, MacOSX/iOS didn't just use FreeBSD's virtual file system, network stack and parts of its userspace at the beginning and sever connections, they continue to incorporate updates (run 'tar --version' on 10.8 "Mountain Lion" and you will note that the libarchive is pretty recent). The Playstation 3 also incorporates code from both FreeBSD and NetBSD.

P.S. The FreeBSD Foundation's fund-raising drive had a target of $500,000 for 2012 but they actually hit $723,379. A large part of this came from the big companies that use their products directly or incorporate FreeBSD into their own products. Some of the big donors include: Netapp, H.R.T., Google, iXsystems, Netflix, EMC2, Juniper, McAfee, etc.

Except that Linux is not Unix by any definition .

Doesn't it have to take great care not to be, for copyright reasons? Don't all those gnu tools have to do the same stuff as their Unix forbears without repeating any AT&T-Unix code?

Quite possibly.
Hey, it's not that I don't think a Linux distro, or all, could be certified as Unix or that I think it inferior (I most certainly don't)*. I was just pointing out that what Linux most certainly is not is Unix.

*From what I can gather Linux follows in the original Unix tradition before the corporations got their teeth into it.

If you see this table

you can see that AIX, Solaris and BSD and HP-UX comes from Unix directly, and Linux is near them. No arrow there between Linux and Unix.

If BDS incorporated code from the original Unix, they would have to pay royalties to the Unix copyright holder. Do they? I don't think so. Beware of what you read in Wikipedia!

The only meaningful definition of Unix is an operating system that will run Unix software. If it runs vi or units, it's Unix. If you are considering desktops rather than servers, then it's something that runs X: that cuts out things like OSX and Syllable.

For a comparison of Linux and BSD usage, see
http://w3techs.com/technologies/details/os-unix/all/all

I am not a lawyer, I just talk like one sometimes .

If it runs vi it is unix?

If it runs something that looks like vi then it is something that looks like Unix.

I used to loosely refer to my AIX machines as "Unix," or explain AIX to others as "IBM's Unix." I would never refer to my Linux setup as Unix, even though so very much of it is indeed a something-that-looks-like

@DavidMcCann: What made you think this had anything to do with copyrights? The Open Group is not (and as far as I am aware, has never been) the copyright holder of UNIX source code. They are however the undisputed UNIX trademark holder and that does give them right to decide who gets to call their products UNIX.

I see in your member info that you run CentOS. Why don't the CentOS team just call their distro "Free Red Hat"? Because trademark law prevents them from doing so despite the fact that the source code is identical. This is exactly why the BSD's and other OS that have some source shared with historical UNIX do not get to call their OSes UNIX without permission from The Open Group.

Have a look around the various BSD websites. You will note that they never call themselves UNIX for the same reason that CentOS does not call itself Red Hat, they do not want to risk being sued by the trademark holder. The most they will risk is statements like, based on UNIX or unix-like, which is not the same as saying their product actually is UNIX. CentOS could also probably get away with saying that their product is Red Hat-like but they couldn't actually call it Red Hat.

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Consider also if I was to setup a restaurant making burgers and I used exactly the same recipe (think 'source code') as is used in a Big Mac. I still would not be able to call my burger's Big Macs or McDonalds would sue me into oblivion. If I struck a deal with them (paid for franchising rights and conformed to various conditions that they laid out), then I could call them Big Macs. That is exactly how trademark law works. If it helps you can think or AIX and MacOS as franchisees of the UNIX brand.

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My assertion that BSD, AIX and OSX share a codebase with Unix and are derived from it doesn't come from Wikipedia, by the way, but from a few historical texts dealing with the birth of Unix.
I'm willing to admit that the actual code shared by them may now be miniscule, a little like a person who changes their broom head and stick and insists it is the same broom. Nevertheless, they're born of the same Multics replacement project.

Indeed they are.

http://www.unix.org/images/chronology_big.gif

I'm pretty sure that there is no original UNIX code left in BSD. IIRC, this was one of the conditions of the settlement between AT&T (who owned UNIX at the time) and Berkeley in the USL v. BSDI (you can find a good write up on that at Wikipedia). Part of the settlement was the release of 4.4BSD-Lite, which contained no original UNIX code. I am pretty sure that all of the modern BSDs are based off of this release. Of course OS X is a rather odd duck, since the kernel is Mach (developed at Carnegie Mellon) with a BSD userland grafted on top of it.

ruario, absolutely pertinent to point out that the copyright in the source code and the ownership of the trade mark are two different things. I'll now retire from "talking like a lawyer" on this --- because I was not good enough at it.

The question of what is and isn't UNIX is pretty silly.

UNIX is a trademarked brand name, owned by someone.

It's like if someone in the 1970s had invented a new tool they called "HAMMER," trademarked and restricted use of the name, and then, forty years later, there were countless threads on hammer enthusiast web sites about which manufacturer's nail-driving devices could properly be called hammers.

Does it have a handle and a heavy head on the end? Do you swing it to strike nails and drive them into wood? It's a hammer, then, no matter what Hammercorp's lawyers say.

Just as the word hammer generically describes the tools made by Black & Decker, DeWalt, and Ryobi, so the word UNIX has come to generically describe Linux, BSD, Solaris, and the like.

It's just an example of a registered trademark finding its way into the vernacular, just like folks from Texas referring to any kind of soda as "Coke."

Certification by the Open Group is, if you ask me, meaningless. We should just add a silent letter to the beginning of the word and be done with it. (jUNIX?)

Anywhere outside of a court of law, Linux is UNIX ... It is, in fact, the UNIX du jour, just as Solaris was fifteen to twenty years ago.