If you look at the system requirements page you'll see, like the error message says, that only Mac OS X Snow Leopard Server is supported and not the Client version, the reason as to why the client version is 'blocked' is not a technical one and is related to the EULAs of these products, you can search these forums for more information on this if you are curious (there are plenty of posts about this matter).
(in case you are wondering about VMWare Fusion, they also block the client version of SL)
Last edited by a moderator: Oct 4, 2013