It's actually got a small companion computer on there, the sonix, which is also running open source code (link) and is responsible for the wifi telemetry and video. Still, it's pretty small and i'm not sure what operating system (if any) is on there so probably not what you need.
The flight controller has I2C and serial ports available although it will require some solding being there are no connectors. This means it is definitely possible to attach other sensors and/or companion computer.
I hope to publish the hardware details of where these I2C and serial ports are on our wiki. I just need the info from @prowse.