> “If you look at the GitHub Terms of Service, no matter what license you use, you give GitHub the right to host your code and to use your code to improve their products and features,” Downing says. “So with respect to code that’s already on GitHub, I think the answer to the question of copyright infringement is fairly straightforward.”

That's assuming that all code on GitHub is uploaded in good faith by the copyright owner, which is not always going to be the case.