Would someone please contact one of the leaders of Github for a comment? Too much speculation going on.
Or the people who asked actual lawyers, and got as a response that this is something that’s very risky.
I’ve got code in my repos from third parties under the explicit condition that I can only distribute it with attribution, so I can’t give GitHub the right to distribute it without attribution in search results.
I can’t grant GitHub rights that I don’t have, what they’re asking of me would require me to do the equivalent of "I’ve got a bridge to sell you".