2 years later: It's now up to the lawyers to figure out if it's the rocket that doesn't meet agreed requirements or if it's on the customer for not giving proper requirements.
I think it is pretty grandma-proof; less is more. Windows xp-like start menu with no web results or other nonsense there, just internet button, picture viewer, and solitaire. Updates can be automated and there's no easy way to break the ui, like accidentally removing the task bar.
If it can't be found online, could start poking with a multimeter.