Microsoft Knowledge Base Article 306578 contains the following summary:
This step-by-step article describes how to either deactivate or reactivate Terminal Services Licensing on a server that is running Windows 2000 Server or Windows 2000 Advanced Server. You must activate a license server before it can issue licenses to Terminal Services client computers. Use Terminal Services Licensing to activate a license server. When you activate a license server, Microsoft provides the server with a digital certificate that validates server ownership and identity. If you use this certificate, a license server can make subsequent transactions with Microsoft to receive client licenses for the servers that have Terminal Services enabled. Terminal Services Licensing has already been installed and activated on the server.