I suggest you contact apple legal.
http://www.apple.com/legal/contact/
I understand that you have to use the server versions of the OS:
10.6 Server license aggreement
"You may also install and use other copies of Mac OS X Server Software on the same Apple-branded computer, provided that you acquire an individual and valid license from Apple for each of of these other copies of Mac OS X Server Software." There is more but you get the idea.
see this page:
http://forum.parallels.com/pda/index.php/t-257976.html
Verify that you virtualization program supports X. You may need to use the VMWare or Parrallels virtualization program.
Don't worry the server edition includes an extra icon on the dock that you can get rid of.
You can install as many client versions of X as you wish on your machine. You need to create a separate partition for each copy of X. You can only run one client at a time. No you cannot run a client in a virtual machine. You can create multiple partitions on the laptop. You could install a diffent OS in the partitions.
Robert