Understand Windows 2008 and R2 license

[guest]

Companies that have already purchased Client Access Licenses or Terminal Services CALs for Windows Server 2008 can continue to use those CALs with Server 2008 R2. Client machines that connect to a Windows Server Foundation machine don't require CALs at all. A license for Server 2008 R2 Enterprise qualifies it to be run in up to four separate virtual machines on a single server (regardless of whether you're using Microsoft's Hyper-V, VMWare, or some other virtualization software), and a license for Server 2008 R2 Datacenter can be used to run an unlimited number of instances on a single server, though it is licensed on a per-CPU basis.