I love these questions bc they both can be answered with some slight heuristics, and they are quite surprising!
As of January 2026, there were > 13k npm packages w/ more than 1 Million monthly downloads [1]
Answering "how many total developers does that cover" is a lot harder (more expensive, rather, as I am not going to pay for the query on Google BigQuery to answer it, not after I spent $3k by accident last time doing similar exploration in the past)
I wont try to make a SWAG about how many devs have write access across those repos, but in the npm ecosystem alone I'm comfortable saying it is an order of magnitude more than 100.
[1] - https://gist.github.com/jonchurch/1dd845f4d26823fce5590af1aa...
NPM probably adds a lot. I can't find any recent sources, but NPM packages get downloaded a lot (e.g., every Github Action run.) And to get such a download, an NPM package just has to be somewhere in the dependency tree, which are famously enormous. (Though many might not be updated in the past 3 months, though.)
[0] https://github.com/search?q=stars%3A%3E5000+sort%3Astars&typ...
I guess I will just have to NOT sign on to this nonsense and allow it to atrophy my ability to think of things independently, thus ending up completely dependent on an outside tool of ever-increasing price.
Gosh darn it, of all the luck.
This is going to get abused so fast, it will make your head spin.
EDIT: I just look up the highest-ranking "buy GitHub stars" page (which I will obviously not link here), and it looks like you would have to pay a little over $1000 to get the required amount of stars. So I suppose it might not get abused as easily as I thought.
On the other hand, someone with the gumption and elbow grease to abuse this process themselves could still easily do so, I'd wager.
All that being said, I still think that GitHub stars are effectively worthless, and attempting to assign value to them like this is, at best, a fool's errand.
I can imagine this will invoke Goodhart's law, increasing the amount of people shilling their AI-generated shovelware onto a Web already greatly suffering from the consequences of the plummeting cost of intelligent-sounding text generation.