This policy setting allows you to specify the RD Session Host servers to which a Remote Desktop license server will offer Remote Desktop Services client access licenses (RDS CALs).You can use this policy setting to control which RD Session Host servers are issued RDS CALs by the Remote Desktop license server. By default a license server issues an RDS CAL to any RD Session Host server that requests one.If you enable this policy setting and this policy setting is applied to a Remote Desktop license server the license server will only respond to RDS CAL requests from RD Session Host servers whose computer accounts are a member of the RDS Endpoint Servers group on the license server.By default the RDS Endpoint Servers group is empty.If you disable or do not configure this policy setting the Remote Desktop license server issues an RDS CAL to any RD Session Host server that requests one. The RDS Endpoint Servers group is not deleted or changed in any way by disabling or not configuring this policy setting.Note: You should only enable this policy setting when the license server is a member of a domain. You can only add computer accounts for RD Session Host servers to the RDS Endpoint Servers group when the license server is a member of a domain.
Windows Components\Remote Desktop Services\RD Licensing
Machine
At least Windows Server 2003
HKLM\Software\Policies\Microsoft\Windows NT\Terminal Services!fSecureLicensing
TerminalServer.admx