While browsing i found an interesting tool in sourceforge.net it says
Mac-on-Linux is a Linux/PPC program that virtualizes MacOS or MacOSX in Linux.
Is it legal? If yes how to install it in Ubuntu?
It's against the EULA, but in general, each provision of a EULA is treated separately (at least, according to Wikipedia), i.e. so a part of a EULA might be found to be legally non-binding. The legality depends on where you are, but if you're in the US, I would guess it's illegal because of the DMCA. Apple sued a clone manufacturer(Psystar) several years ago for selling machines with OS X installed on them. They sued under several different legal reasons, but one of them was that Apple uses encryption methods protected under the DMCA to keep OS X from being installed on non-Apple hardware. The court found that indeed the DMCA was violated and Apple won.
It is definitely a EULA violation. Violating a license agreement is like violating a contract. It gives Apple the right to sue you. Will they? Probably not. As long as you aren't getting in the way of their business. So is it illegal? I would say yes. Is it criminal? No. It's simply a civil contract violation. You have to make up your own mind. Personally, I suggest just getting some Apple hardware because it's great.
Legal or not is a grey area for OSX on non-Apple hardware. I think, for personal use, the most that will happen is that they won't give you tech support
Mac on Linux works on PowerPC processor. It is not designed to work on x86 processor family. In practice, the question is "Is it legal to run Mac On Linux" on old Apple Hardware? Apple stops PPC in 2006 !
I have an old PPC iMac, and I tried installing Ubuntu on it. It sort of worked, but barely, and a lot of programs won't run - even things like Google's Picasa requires an Intel CPU. Yellow Dog Linux is about the only supporter of Linux on PPC these days, and it's not easy to get it working.
So, finding non-Apple PPC hardware, and then getting Ubuntu to run on it would probably be harder than any potential legal battle with Apple. :)