Well, theoretically you could make an implementation which reads the QR code then displays what would have been posted to the server. Via a web-browser extensio

Well, theoretically you could make an implementation which reads the QR code then displays what would have been posted to the server. Via a web-browser extension, you could then type this into a form field and have that log you in. You could base<something> encode it to make it a little easier. So, it seems feasible offline with online required only for convenience.