BeOS was a commercial product, and was very poorly marketed and treated like a bastard child by the company that developed it; they were more intent on concentrating on the integrated market (think palm pilots, etc) but that did not pan out for them.
There is a new commercial product called Zeta, based off BeOS which you can pay to run. There is also a project to rewrite the operating system, making it compatible with all that old software for it out there called Haiku.
More interestingly, free, and currently working is BeOSMax. Be Inc. in an effort to raise awareness of their OS at one point released a 'Personal' Edition for free. If I recall (it was a long time ago, and my memory is fuzzy) you could install it on a Windows partition as a file and it would pull some tricks to boot into the operating system. You could not install it on an NTFS partition and you could not actually install the operating system on it's own partition; to do that you would need to buy the OS.
Enter BeOSMax; they've hammered chizzled and busted up the OS enough to have an installable version of the OS, along with nice features like Firefox 2.0, a word processing suite, and a game you all might remember called Doom, which runs just fine, even in a VMware (which you can also download for free...) virtual machine.
This concludes "You things you might want to play with on a boring weekend"
