For what it’s worth, github signup for this talk seem not to be working, at least for me.
When you click the “with github” link on the signup page, a popup opens which almost immediately shows:
Sorry, there was an error authorizing your account. Perhaps you did not approve authorization?
I never got any chance to approve anything.
Finally I signed up the old fashioned way and when I clicked on the email link and then clicked the “authorize …” button on the page that opened, it gave me the same error (although as this post showed it still seems to have worked behind the scenes).