Is buying apple operating systems illegal?

[WhereHere1]

I had my thread closed because I asked how to change from a windows operating system to an apple operating system.

So I have some questions:
-is installing apple operating system on a home built computer illegal?
-isn't Linux just the operating system for apple?
-I thought the apple OS for anyone to use was widely available?



Please not I am not interested in any cracked software.
If genuine software is available on overclockers I will buy it.

I feel my last post was shut down a bit premature.