Its the same as other user generated content sites... The ToS is to legally shift blame from GitHub to the users... and thats what made me think of "code id" actually, since GitHub have a firm defence in the form of "Users doing illegal things isn't our fault, we asked them not to and tried to kick people off when we found out they were violating the terms, but they might still get slapped around a bit by the Court and need to implement some form of safeguards the way YouTube was forced to, because your point about how binding the terms of service are when the consideration is "use of this service in exchange for agreement" is true, there is not a super strong contract here, its nominally more binding than the average clickwrap contract pre-install EULA since the consideration in exchange is use of the service itself, but as case law around things like scraping and other internet activity has shown, its definitely not as binding as a physically signed sale contract would be...