[Ricapar]

It's not just the visuals either - they have a bunch of the apps down really really well.

Finder, Calculator, Calendar, the top menu, etc. All really spot on.

I'm playing around in it still. Managed to find my way to the Terminal, and I'm poking around the filesystem.

It is Linux, and seems to be based on a stripped-down version of RedHat (going from some of the remnants of certain man pages).

The UI is a modified/themed KDE.

They did a really good job with the apps - for example, the calculator app is "Calculator.app", which is really a directory with a Contents/Resources, etc directories inside it; the same way OS X does it.

[dippyskoodlez]

It would seem like they used Red Hat for the SE Linux implementation(?) but should have just used BSD.