Link Here for more Info: http://www.microsoft.com/servers/hyper-v-server/how-to-get.mspx
Download Microsoft Hyper-V Server 2008 Today!
Licensing Microsoft Hyper-V Server 2008

Microsoft Hyper-V Server 2008 is a stand-alone product that will be available via the Microsoft Download Center free of charge.
Microsoft Hyper-V Server 2008 does not require CALs for the product itself.
CALs will be required for all Windows Server virtualized operating systems [...]