Site Licensing Servers are a feature in Server 2003 that doesn't appear to exist as an actual service in Windows 2008R2.
Does this service still exist? Is there any benefit to this at all?
If you setup an internal KMS server, it will use the software license service in 2008 to manage and activate your Microsoft Volume Licenses. The benefit of using an internal KMS is the workstations and applications (Windows/Office/etc) do not have to contact Microsfot's servers for activation so long as your KMS server is properly licensed.