Ah, you have a quote right above that line stating it is the firmware that is non-free; hardware isn't mentioned. You might want to edit your original post so it is consistent with what you are trying to communicate.
Ah, my bad. Unfortunately I can no longer edit the comment...
No worries, the edit cutoff has bit me before as well. But just to clarify, you do mean that the hardware is closed source, and the firmware is not? I did see some licensing stuff on prusa's GitHub, looks like they have non-commercial licensing for their graphics package.