You can do it legally. If you have a current Mac, that is. You'd have to buy a retail version of OS X leopard and patch it on your real mac. That part is legal. The part that falls into a grey area is installing it. Although you are not breaking any copyright laws (not that you care, at least I do), you break the EULA which states that you must install it on Apple Branded hardware. I haven't done this. But it is possible. Just google OS X x86 or something like that. (the OS and the x86 parts are pretty important 😉 )