This post is for administrators who want to control which Remote Desktop Session Host (RD Session Host) servers are issued Remote Desktop Services client access licenses (RDS CALs) and which version of RDS CAL is issued to the RD Session Host servers, and discusses how to control the auto-discovery of a license server running Windows Server 2008 R2 from terminal servers running Windows Server 2008 or Windows Server 2003. “For security reasons, you might want to specify the RD Session Host servers to which a license server offers RDS CALs. You can apply the License server security group Group Policy setting to a Remote Desktop license server to control which RD Session Host servers are issued RDS CALs by the license server.”

Full Article: RDS blog