The OTP ROM is programmed with a token intepreter. It cannot be reprogrammed. The tokens are stored in an external serial EEPROM. The PC software converts the BASIC program into tokens, which are then downloaded and stored in the SEEPROM.
An unprogrammed MCU will not work. You can probably buy chips with their proprietary program from the maker (Parallax?). Naturally, they will have protected their program so you cannot simply copy it.
Best regards, Spehro Pefhany