Why would they think this was a good idea after losing the chrome anti-trust trial? I don't know the intended purpose is for this, but I can see several ways this could be used anti-competitive way, although now it has been reverse engineered, an extension could spoof it. On the other hand, I wonder if they intend to claim the header is a form of DRM and such spoofing is a DMCA violation...
x-browser-copyright seems like an attempt at something similar to the Gameboy's nintendo-logo DRM (wherein cartridges are required to have the nintendo logo bitmap before they can boot, so any unlicensed carts would be trademark infringement)
http://en.wikipedia.org/wiki/Sega_Enterprises_Ltd._v._Accola... is the legal precedent that says trying to do that won't work, but then again maybe Google thinks it's invincible and can do whatever it wants after it ironically defeated Oracle in a case about interoperability and copyright.
Apple famously does this with this word soup in their SMC chips, and proceeded to bankrupt a company that sold Hackintoshes and shipped it in their EFI: https://en.wikipedia.org/wiki/Psystar_Corporation
Our hard work
by these words guarded
please don't steal
(c) Apple Computer Inc
Though one could argue that they would have probably bankrupted them anyway even if they hadn't done that.
not if they make it dynamic somehow (e.g. include current day in hash). Then with MV3 changes that prevent dynamic header manipulation there is no way for an extension to spoof it.