Q: Do I need to buy an RDS CAL to remotely connect to my desktop over Remote Desktop Protocol?

A: The Remote Desktop Connection capability is a feature of the Pro, Ultimate, and Enterprise editions of Windows 7, and included in that is the right for the primary user to connect to that desktop remotely. A separate RDS CAL isn't required for this type of connection.

An RDS CAL would be required if any RDS role was used as part of the connection, such as if the desktop was hosted as part of a virtual desktop infrastructure, or if you're using Remote Desktop Connection Broker, Session Host in redirection mode, RemoteFX, or any other RDS component, including Remote Desktop Gateway.