We have changed the configuration of our DV3000 add-on board to use the same 26 pin header as the Raspberry Pi. The boards are working in the lab now and are headed off for application integration. Two thirds of our pre-orders expressed interest in D-STAR and half of those would like the add-on board as well.
The AMBE3000 chip only requires the Mini-UART interface, leaving the Pi's I2C and SPI interfaces available for other purposes. RESET is on IO18 and RTS is on 1O17 (There is no CTS).
If you're a Pi developer and have interest, we may have a few units available for early access.
Send an email to support@... and tell us how you would use it and what open source software you would port or write.