If an RFB program connects to a Windows Terminal Server using the RFB protocol it is probably because it is running a RFB service like VNC and not the Terminal Service.
Unless that is a typo and you ment to say RDP. Tom I could be wrong, but I believe the RFB program and krdc (which is included in Red Hat and Fedora) can connect to Windows Terminal Server using the RFB protocol, or other Linux machines using VNC. Warren
