Oh god that's so rough, it looks like they're (very poorly) using an angle grinder free-hand and an oxy torch to cut out their plates.
They'd probably find the tooling and jigs they need to do the job properly would be much cheaper and easier if they didn't go way overkill. This little engine does not require a huge 1/2" thick steel plate to mount it on.
Overall, this site https://wiki.opensourceecology.org/wiki/Main_Page is much better than the linked one for overall information about this initiative, for example https://wiki.opensourceecology.org/wiki/Power_Cube_Design_Ra... .