This development cartridge seems to have been used by The Code Monkeys and is Accolade made. Lots of epoxy all over the chips to make it hard to repair / reverse engineer. Certainly is a pain, but it may have been like that also to prevent damage. A few of the capacitors on the front of the board have come loose, probably due to getting stuck on the door flaps of a Mega Drive a few to many times. If you know anything more about this cartridge, please do leave a comment here or on the YouTube video.
Above is the card itself, quite fashionable given it is from a third party publisher.
The intro that appear when the cartridge is inserted into a working Sega Mega Drive.
Finally we have the Accolade silkscreen on the PCB that was blacked out with what appears to have been a marker pen.