This is a board designed to provide all the usual needed ports in one place, on one I/O port and with the minimum amount of logic, in particular avoiding expensive and/or CPU vendor specific devices. It's loosely based upon Lee Davidson's 6502 bitbang PS/2 keyboard interface except that it tries to support a mouse as well. The spare input and output bits from the latches and buffers used also drive a basic 4 bit audio interface and a simple joystick input.
The prototype had a few errors and needed some extra wiring but the 0.3 version appears to be working correctly.
Audio jack is part number CUI SJ1 3533NG