Hi, I don't know what is the status on supporting multitaps. But I found this documentation from a guy who manufactures multitap2usb chips:
http://www.raphnet.net/divers/documentation/genesis_multitap.txt
This seems pretty complete, with source code etc. Any hope to be able to plug a Megadrive multitap into a Retrode someday?
Also I remember you were looking into the J-Cart (Micro machines, Pete sampras Tennis) to try to make it work. Any success?
A definitive no to both, I'm afraid. The Retrode hardware doesn't provide some special signal wires - if anything, a user modification would be required.