フォーク
Fork a repo – User Documentation [Official]
Forking Projects · GitHub Guides [Official]
コピーライト表記
参考：
Co-authors
参考：
Creating a commit with multiple authors – User Documentation [Official]
Commit together with co-authors | The GitHub Blog [Official]
Commiter/Contributor
What is the difference between a committer and a contributor in GitHub? – Quora
Contribution Guidelines
参考：
Setting guidelines for repository contributors – User Documentation [Official]
How to Contribute to Open Source | Open Source Guides
Contribution Statistics
Git – show statistics for authors contributions – Stack Overflow
git-stats
IonicaBizau/git-stats: Local git statistics including GitHub-like contributions calendars – GitHub
License
Adding a license to a repository – User Documentation [Official]