I recognise this is a bit thread-dredgy but I'd like to see this initiative brought back to life.
I've created a GitHub project for an Arduino Due based CAN gateway. The idea being that those of us with development skill can contribute either in the form of decoding the bus messages, or helping optimise my (probably rather amateurish) codebase.
The hardware this is designed for is the CopperHillTech jcom.can.due.
Endgame would be to be able to opensource a CAN gateway that could be used to translate between any factory or aftermarket ECU and the BRZ/GT86/FRS CANBUS in a flawless manner. It's doable, but we need to work together.
https://github.com/wiretap/brz_cangateway