[benfrederickson]

I just saw your question on proggit, and I lazily cut-and-paste the answer for here =):

For your first question - yes this means few people use more than one language in a month. There is also a power law distribution happening with user activity each month, so most users only have a handful of events each month (which happen to be mostly in a single language). I'm trying to measure how broad support it so this was mostly done on purpose. I was finding counting total events was getting biased by things that I most have been automatic activity (I was seeing single accounts with 10K commits a day for instance).

Percent of MAU in the charts is the total percentage of unique users who were active that month. I haven't tried out with yearly active users =(