Terminal Services CAL
The Terminal Services functionality is included with the acquisition of a Windows Server 2008 Server License. However, when a user or device accesses a terminal server, that user or device is required to have a TS CAL (in addition to a Windows CAL) in order to be compliant with the licensing terms of the product. A separate TS CAL is required for each user or device that accesses or uses the server software on any server.

Device CAL
A Device CAL permits one device (used by any user) to access or use the server software. Device CALs are likely to be more cost-effective than User CALs if there are multiple users per device (for example, a call center or an airport kiosk).