That's not obvious, because you don't necessarily own the code you're uploading. I can upload any sort of MIT-licensed, BSD-licensed, Apache-licensed, Creative-Commons-licensed, or GNU-copylefted works I want, anywhere within reason and compatible with those licenses, but if I didn't write them then I don't have the legal right to relicense, grant exclusive or restricted license to any specified parties.
So in a way this would void parts of many TOS agreements where you do relicense your User-Generated Content. If we're uploading memes to Facebook, they're gonna have to work out license terms with the copyright holders, not the uploaders.