Hardware wise, the schematics are available but not under an open source license (commercial use prohibited), as far as I know PCB layouts aren't. Not sure about the case.
Software wise, the closed source parts are the OMAP boot ROM (virtually unavoidable), WiFi module firmware, PowerVR libraries and firmware if using 3D, modem firmware (but there is a switch to kill modem power) and eventually (not in the current OS) audio offload DSP firmware.
Hmm, I don't have anything like that in my archive of pyra materials. Plenty of renders from various points, but nothing I'd class as a design document. I've no real idea how thick the walls of this device will be for example, beyond being sufficient for purpose, thanks to ED's diligence.