Contributor
Someone whose changes were accepted into a repository they do not own. GitHub lists contributors on every repository page.
What it tells you about a developer
The contributor list on a project a strong candidate works on is a ready-made list of other developers in the same technology and skill range.
A contributor sent a change, called a pull request, and a maintainer reviewed and accepted it. The repository's contributor list is ranked by how much accepted work each person did. Looking at who else contributes to a project a candidate works on surfaces other developers active in the same codebase and technology.