Running MacOS X as guest in VirtualBox

I have been looking for a while for a solution where I could easily work with MacOS X on my workstation. I am currently running Ubuntu, with a virtual Windows XP in VirtualBox for Photoshop, Flash and some other Windows-software.

Since the MacOS X runs on the x86 architecture these days, I figured I should be able to run a virtual MacOS X as well.
However after some looking around, it appears not to be possible. And it's not a technical problem, but rather a issue of the MacOS X EULA:

"This License allows you to install and use one copy of the Mac OS X Server software (the "Mac OS X Server Software") on a single Apple-labeled computer."

The only solution for now appears to be to use VMWare together with a cracked version of MacOS X and follow a long series of installation instructions.
However, this is not a working solution for me, since I prefer to use the open source VirtualBox rather than the commercial and NSA funded VMWare [1, 2].

There is some discussion in virtualbox.org regarding MacOS X guest support, but Sun appears to officially ignore it (the OS is not even listed here for example).