Good - at least the fact that I'm learning Linux commands and operating systems will help if I ever trial the bigger UNIX.

From what I can see Open Solaris tales 500MB RAM at idle, which is too much for my laptop at the moment, unless I upgrade. I want to be running max 350-400MB at idle. Ubuntu's very conservative at <200MB at idle.

BSD looks good to experiment with, but the installation procedure is a test in itself and not at all user friendly. However, it has very small RAM & HDD requirements, so I'd probably be after a low footprint application.

For a low footprint OpenSolaris based distribution, you may want to try milax: http://www.milax.org/

Thanks- I'll give this a try...

No actually Linux is a unix-like operating system. BSD was derived from the original unix implementation but Linux was a separate independent implementation

I'll add more =)
*BSD comes from 4.4BSD - UNIX
Solaris and SunOS are UNIX
HP-UX is UNIX
AIX is UNIX
IRIX is UNIX
OS X, born of Darwin born of born of NeXTSEP born of Mach born of 4.2 BSD, is UNIX

Simplifed timeline (Warning, big image).

Solaris is a registered UNIX product, conformant to the Single UNIX Specification (UNIX 03) standards.
Linux and *BSD are compliant with a lot of standards, but it costs money, etc. to have something registered as even POSIX-conformant, and POSIX is only a part of the larger Single UNIX Specification standards.
Linux and *BSD, in any documentation or anything, will be referred to as a UNIX-like operating system.
Solaris is UNIX
AIX is UNIX
HP-UX is UNIX
etc.
OS X (as of Leopard, I don't know if they were before) is using a lot of FreeBSD, and the Mach microkernel. It is a registered UNIX product, conformant to the Single UNIX Specification (UNIX 03) standards, just like Solaris and AIX, and HP-UX, etc. Mac OS X Leopard uses a lot of FreeBSD and also GPL'd software ... they have a modified version of gcc, etc.
CNET - Apple being sued by The Open Group
The Open Group
Register of certified products
Apple page mentioning features of OS X.

I don't remember who made the sarcastic remark, "The great thing about standards is that there are so many of them." This is true about Unix standards as well.
There are a number of functions, such as getconf, pathconf, fpathconf, sysconf which can help in sorting out the mess.
Two different Unix OSes can vary more in some areas than a "Real" Unix and Linux.

Here's the soap...

In the mid-1970's (heh... I was there...) the MULTICS project was a spectacular disaster, of the sort that only a government committee could produce. And so, a bunch of Bell Labs folks who just happened to have a PDP-7 on their hands decided to see what they could do with it. They came up with a little toy of a system they tongue-in-cheek called "Unix." (Multics...Unix... get it?)

Because AT&T was at that time a government-run monopoly, they had to release the source-code of Unix. So they did.

Fast-forward twenty years to a college kid who's freezing his butt off in Finland while hacking operating systems. To keep himself warm, he decides to build "a little x86 OS of his own." And he releases that source code to a Usenet news-group.

The system that Linus Torvalds bases his work upon is Unix ... but, having none of the source-code to the actual Unix system he works instead on a "fairly 'toy'" implementation of the POSIX standard. He employs a rather stunning collection of software tools, called "GNU," which had been pioneered by another rather amazing hacker, Richard Stallman.

And... it just happens to be "the right thing at the right time." From this tiny germ of an idea, and with the combined efforts of literally thousands of engineers throughout the Internet, a very full-featured operating system is created. It isn't Unix, but it follows closely in that system's footsteps.

As time goes on, "the dragon has eaten its tail." Engineering is like that sometimes.

AT&T was a monopoly, but not government owned. Due to an anti-trust ruling, they were not allowed to sell an operating system. So they developed Unix at Bell Labs for in-house use, to process patent applications. Because they couldn't sell it, they gave it away to some Universities. Because of the variety of main frames and mini's in use at the time, even propriety software was sold in source code form. When AT&T was broken up, the prohibition against selling operating systems was lifted, and Unix became a commercial propriety operating system.

Unix was not just used internally or by universities before AT&T was broken up. Several commercial proprietary operating systems based on Unix version 6 and 7 code were already sold in the late seventies and early eighties.

Linux is not based on Unix at all, as many folks tend to think. (lack of technical knowhow, and media influenced that are wrong)
Linux is based on Minix, which is on itself based (partly) on Unix.
So, linux is the so called third generation of the family of Unix, but not a direct member, that is minix.

You need to clearly define "based on" with such statements.

If "based on" means "based on concepts from ...", Gnu/Linux and Minix are both purposely based on Unix by design.

If "based on" means "based on code previously written in ...", Gnu/Linux, Minix and Unix are independent of each other and share nothing in common.

If "based on" means "was originally coded on machines running ...", then Minix was based on Unix, the Gnu stuff was based on Unix and the Linux kernel was based on Minix.

Minix isn't a direct member as you wrote, perhaps are you confusing with BSD which has its roots in Unix code.

This is what i ment indeed. And since linux is strict speaking the kernel only, it's based on Minix. (thus not Unix, strict speaking) :-)

teebones ...
You're saying that if something is "based on" Unix, then it's Unix ... If something isn't "based on" Unix, it isn't Unix.
It's all "based on" Unix.
FreeBSD is not recognized as UNIX. It is not conformant to the Single UNIX Specification (UNIX 03) standards. The official FreeBSD site refers to it as a UNIX-like operating system.
This is a quote from the freebsd.org about page, found here:
^"derived from BSD"^
This is a quote from the official Minix site:
^"UNIX clone"^

Apple's Mac OS X is a registered UNIX product (Single UNIX Specification standards, UNIX 03). It is "based on" the Mach microkernel and FreeBSD, along with other things like a modified gcc, for example.
Look here. Quote:
Not UNIX 03, but POSIX compliance is very widespread. FreeBSD, Linux, etc. POSIX is part of the SUS standards.
The Mach microkernel is also "derived". It's not UNIX.
The "not-recognized-as-UNIX" Mach microkernel and "not-recognized-as-UNIX" FreeBSD components, along with modified gcc, and other GPL'd software, and whatever Apple's done with them, make up a "recognized-as-UNIX" operating system. Today.
The fact that FreeBSD is derived from UNIX doesn't make it UNIX. It's not pre-standards UNIX, either.
Today, POSIX and SUS standards are used to recognize UNIX products. POSIX standards are part of the SUS standards. You can find POSIX compliance in everything. Also, the fact should be mentioned that GNU Hurd uses Mach.
http://en.wikipedia.org/wiki/POSIX

Also, I've read about today's UNIX operating systems. Moving from one to another can cause you headaches, and they're UNIX - standard UNIX - SUS UNIX 03 standards conformant UNIX operating systems.