This is really neat and I love playing with stuff like this. But, fundamentally, it shows that stars aren't a good measure of anything besides stars, at least outside of the top scorers for commonly used languages. For those, it's not a bad proxy for fame.
If you like at the top javascript or ruby developers, yep, those are all pretty famous javascript and ruby developers. But if you look at the #6 matlab developer, well, turns out that's me. I've probably used matlab for less than 40 hours total, lifetime. And most of that was in grad school, a decade ago. Most of my stars come from a tutorial. Not a tutorial I created -- a tutorial I worked through, that thousands of people have probably done. Ok, so, not many people put matlab code on github, so that data is messy. What about popular languages?
Turns out I'm also the 240th most starred scala developer worldwide. I once used scala for two months and created some projects to help me learn that aren't even close to being polished enough to be useful to anyone. Like most code written by someone who's learning a language, it's not any good. But that somehow puts me at 240? Even in a pretty popular language, by the time you get into the hundreds worldwide (or the top few in most cities), it's people who just threw up some toy projects.
I wonder if this explains why I've been getting recruiters contacting me "because they saw my scala code on github". I doubt anyone who's actually seen my scala code on github would contact me for a scala position, but someone who uses a tool that counts stars might think that I actually know scala and contact me for a scala position. This particular tool is too new to be the source of that, but the page the source data comes from (github archive) shows how easy it is to make BigQuery queries to return results like this.
For Julia, I'm also presently ranked above all of the co-creators of Julia, despite having spent a total of perhaps 20 hours ever using the language (I'm 72, compared to the co-creators, who are 113, 143, and unranked).
BTW, in languages I've actually worked in professionally, I'm 98,582/244,375 in a language I used for years before it became trendy, 1,100/1,835 in a language I've used a lot recently, and 75,998/161,465 in a language I've used some recently. In the language I'm most proficient in, the language I'm mostly likely to reach for if I just want to get things done, I'm 14,800/25,094.
P.S. If the developer is reading this and wants bugreports, your service returns a "503 Service Unavailable" if you click the "top foo github developers in your city" for developers that don't have an associated city.