Out of curiosity I tried using the XTB-XM with Home Control Assistant (HCA) and a USB to serial port adapter. It would not establish communication with the XTB-XM. I eventually tracked that down to HCA requiring the GET_IM Configuration and SET_IM Configuration commands. While these bits only relate to Insteon operation, I added a configuration byte in the version 1.01 firmware, and now it is working fine as a 2413S with HCA for X10 devices.
But so far there has been virtually no interest in this project.
Jeff