Contributors
Grit is one maintainer and a short list of people who have shipped code into it. The list is short on purpose: it is read off GitHub rather than written by hand, so nobody is on it who is not.
Commits are not the whole list
GitHub counts commits, so the numbers above undersell almost everybody but the maintainer. The clearest example is on this page: daljo25 shows one commit. That commit is grit setup, and before it they filed the issue that became grit plugin new and made the argument for building it as a command rather than a template repository, which is the reason it works the way it does.
Pull requests
The part that counts here. Read CONTRIBUTING.md first: it is short.
Issues and reviews
A well-argued issue has changed the shape of this framework more than once.
Bug reports
Especially from a real project. Those are the ones that find what tests do not.