IANAL but I believe you are incorrect about the rights you grant GitHub. They are still bound by the license you set in your repository, including any copyleft

IANAL but I believe you are incorrect about the rights you grant GitHub. They are still bound by the license you set in your repository, including any copyleft in GPL or attribution requirements. GitHub TOS sections D.4-D.7 spell out the license that you must grant GitHub in order to host code there. “You grant us and our legal successors the right to store, archive, parse, and display Your Content, and make incidental copies, as necessary to provide the Service, including improving the Service over time.” Notably, see also section D.3 which states “If you upload Content that already comes with a license granting GitHub the permissions we need to run our Service, no additional license is required.” I would think any open source license would be sufficient license for those things, like storing and displaying code, and I would think this clause is primarily for code without a clear license not already granting these terms. To your point about redistribution, see this clause in D.4: “This license does not grant GitHub the right to sell Your Content. It also does not grant GitHub the right to otherwise distribute or use Your Content outside of our provision of the Service, except that as part of the right to archive Your Content, GitHub may permit our partners to store and archive Your Content in public repositories in connection with the GitHub Arctic Code Vault and GitHub Archive Program.”