"If You institute a revocation of a GitHub star against any entity (including cross-repository and cross-user removals) alleging that the Work or a Contribution incorporated within the Work no longer constitutes a GitHub star, then any patent licenses granted to You under this License for that Work shall terminate immediately as of the date such a revocation is performed."

I've seen this on a lot of the hacktoberfest repos this year. The repo owner will only authorize the PR if you star them