I haven't looked at the GitHub API in a long time but I wonder if it would be possible for a 3rd party to replicate this functionality using the GitHub API.
Yes, quite easily I’d suggest. I’ve built a GitHub analytics tool on top of their api. Primarily for internal metrics & tracking community engagement. The api makes a lot available, it’s very open. For public repos you can get lots of stats around activity and community engagement that would enable monitoring/projecting growth.
