1. VMware is just now starting to support running Mac OSX in a vmware image. Currently only Lion is supported, but I read today that they will be enabling Snow Leopard support as well. 2. You can only run a Mac OS in a virtual machine that is running on a physical Mac. You can't just run it in a vmware image that is running on a Windows, Linux, or other machine. 3. As you surmised, the guest Mac OS has to be properly licensed.
That said, there are people who have cracked OSX so it can be run in just about any suitable VM environment; however, these are NOT licensed hacks and support is pretty non-existent. If you are interested in that, you might try a Google search.
Well, it does make some sense, in that you can run older/different versions of the OS, or use the virtual machines to isolate applications from each other, or for development and testing of kernel components that may crash the host OS if not run in a VM. I run Linux virtual machines on my Linux system for just such purposes, along with other operating systems such as QNX, Solaris, and Windows.
There is also Hackintosh, an OsX which you can install on a "non-Apple hardware". I was trying it when lion came out, but Snow Leo had no stable drivers (kexts) for my x64 PC, and Lion was still unusable. Should retry soon...