I think the activity in an open source project is a very useful metric, but unfortunately it's non-trivial to measure "activity" - it is indeed needed with manual work here, for many reasons ...

• Some developers may spend ten commits doing what other developers do in one commit - and there may be different reasons for that.

• GitHub is a commercial company, their services are great, but they do not have some kind of monopoly when it comes to hosting open source products. There is gitlab and bitbucket, for instance ... and people may forego such services at all, hosting the necessary infrastructure themselves.

• The assumption "one currency one open source project" may be wrong.