Ask HN: What is the best metrics for open-source startups

A large and engaged developer community can be instrumental in building a successful open-source startups. Thanks to Github, it is possible to assess the popularity of repositories (by stars &forks). One the most interesting developments in that field is ROSS Index: the top open-source startups by their star growth. https://runacap.com/ross-index/

What other battle-tested metrics for open-source startups can be valuable?