So someone steals my source code and posts it on GitHub, now i no longer have copyright rights?
The duty is on the copier to ensure they are granted a license.
Open source projects on GitHub rely on D6 section of GitHub TOS. That is the part where a user declares that when s/he makes a contribution to a project, s/he does so under repository license. Also that you have right to do so (e.g. when you are on employer clock, your employer must agree).
It's not just a duty of copier to ensure they are granted a license. Legal stuff is never clear cut, but if someone agreed to TOS, it should be generally (that's a funny word that can mean anything) safe to assume that s/he does abide by it.
In this case, there is an obvious conflict and when there are two conflicting clasuses... that's fun for laywers.
That's obviously not the case. GitHub even has their DMCA takedowns public. You can't redistribute copyrighted material unless it's under a license that allows for it.
