Supposedly Gentoo has one.
What a lot more people seem to do, if they want to play around with open source software, is to not use Linux, but use Fink to install KDE or Gnome or whatever window manager they want on top of OS X (since OS X is already a Unix basis, and it even already has an Apple-distributed X-windows manager, there's no reason you can't run KDE or Gnome on top of the "Darwin" part of OS X instead of the OS X Aqua GUI).
You can google for this... here is an example walkthrough:
http://www.appletalk.com.au/articles/index.php?article=12088
FWIW I don't think you're constrained to having the X environment in a window like they show it. I know Apple's X manager allows X to go full screen.
Once you're running KDE and X on top of Darwin, and you use Fink to get packages for the standard Open Source stuff, it really will be so much like using Linux that you might find you don't need to bother with live cd's.
😉
But then again, of course, it might not.