Other than that, this is an interesting idea. Obviously it is going to be pretty inaccurate because it is just one guy's opinion. I wonder if you could construct a similar graph based on actual measurements of people's Github commits or Stackoverflow questions.
While you are technically correct, I think the distinction between server-side and client-side matters here.
Many people started with javascript out of necessity, but then began using it in many areas outside of scripting for web pages. And server-side JS is very different than client-side JS in many ways.
Take something like Ruby for another example. I wouldn't find it out of place to see something like this with "Ruby [without rails]" and "Ruby On Rails" listed as 2 different things.
Other than that, this is an interesting idea. Obviously it is going to be pretty inaccurate because it is just one guy's opinion. I wonder if you could construct a similar graph based on actual measurements of people's Github commits or Stackoverflow questions.