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Can you help me with my software licensing question?
Assuming I have some appropriately licensed virtual machines running in a Server 2008 Hyper-V host, do I need to purchase extra Client Access Licenses for the host? Is there a significant difference in the licensing between Hyper-V and Virtual Server 2005?
According to this page, if your Guest OS's are server 2003 or 2000, and your Host is only running virtualisation services then you do not need Server 2008 CAL's for the host. If the guest OS's are server 2008, or the Host is running any other services, you will need server 2008 CAL's for the host.
It's a bit of a confusing setup really. I would suggest you contact MS licencing for a more detailed respsonse (in writing if I were you!) their usually pretty good.
Under normal circumstances, you get one CAL per user or per device on your network; you really don't want to deal with the complexity of per-host CAL licensing. Really.
If you have Windows 2008 CALs for all your users or devices then you don't need anything extra for your VM host, but you probably know that already.
A user/device accessing a non-2008 VM that is hosted on a 2008 server does not need a 2008 CAL. If the guest OS is a Windows Server OS, then they need a CAL for that version of Windows.
If your situation is like ours - lots of 2003 CALs, no 2008 CALs, no SA, then yes, you can run 2003 servers virtually on top of 2008 Hyper-V; just get enough 2008 CALs for your admins.