OSPi 1.4 Plus can work with RPi 2 and RPi 1 A+ or B+. It however, doesn’t work with RPi 1 A or B — although the pins are still compatible, they can’t fit into the enclosure and the PCB cutouts. So if you want to use OSPi 1.4 Plus with RPi 1 A or B, you will have to use a ribbon cable to make the connection.
Partly the reason we discontinued the OSPi 1.4 Standard version is the fact that RPi 1 A or B is becoming increasingly obsolete, and the form factor is different from all the newer models including A+/B+/RPi 2.
I know this is an old thread, but you can remove the composite video and analog audio connectors from an RPI 1 Model A or B and they’ll fit into connectors designed for 2+ RPis.
There is still an issue with the USB ports being further out from the board, so if you install even a micro-WiFi it will not fit in the default case, but you can cut space for it without too much trouble.