This is an inverted version of the default Donkey Raspberry Pi mounting plate and camera mount. It is inverted so that the electronics are mounted below the plate when installed and the original vehicle body can be installed. It also makes for easy access to the uSD card for easy removal and insertion.
It does use the a feature from the MCAD utility package so you'll want to download and install that. You can get it from here: https://github.com/elmom/MCAD