There are a lot of metrics which are not covered in this article.
For example, I think that having a lot of one-time contributors with small PRs is actually a sign of good health; it generally means that the project's code is stable and easy to read and modify for newcomers.
Also, I don't think that the number of commits or commit frequency has much to do with project health; low commit count could simply mean that the project is very stable; which is usually a good thing... Sometimes you don't need more features.
I think that when the project is still evolving, it's better to only have one or two main contributors - Otherwise the project's vision and direction can be lost.
I think that Redis is a perfect example of a healthy OSS project. The contribution stats on GitHub look ideal to me: https://github.com/antirez/redis/graphs/contributors
Also, I don't think that the number of commits or commit frequency has much to do with project health; low commit count could simply mean that the project is very stable; which is usually a good thing... Sometimes you don't need more features.
I think that when the project is still evolving, it's better to only have one or two main contributors - Otherwise the project's vision and direction can be lost. I think that Redis is a perfect example of a healthy OSS project. The contribution stats on GitHub look ideal to me: https://github.com/antirez/redis/graphs/contributors