Just wondered across wing while looking into some potential shady self-promotion on Reddit. Ignoring the mixed-licensing of the project, most of it is under MIT for which they point to a Contributor License as part of their PR template, which is opt-in via open of PR.
They also have a bonus “Contributors Terms of Service” which assigns rights (5.2) while additionally having this fun mechanism of acceptance (1.2):
BY CLICKING THE BOX INDICATING YOUR ACCEPTANCE OF THIS CTS, BY CONTRIBUTING ANY CONTENT TO THE PROJECTS OR BY OTHERWISE PARTICIPATING IN A PROJECT, YOU ACKNOWLEDGE THAT YOU HAVE READ AND UNDERSTOOD THE FOLLOWING TERMS AND YOU AGREE TO BE BOUND BY THEM AND TO COMPLY WITH ALL APPLICABLE LAWS AND REGULATIONS REGARDING YOUR PARTICIPATION IN OR ENGAGEMENT WITH THE PROJECT […]
Overall it’s about 4.5k words to read before contributing.