So, super obvious, but thought I'd just mention that influxdb is open source. It's likely that free version helped the contributor with his issue so he contributed back.

You don't think the enterprise users can use his work?

The implication of an MIT license is that anyone can use or sell your work with attribution. If the contributor was not happy with that, or unhappy with getting a free db worked on by other people, they simply wouldn't contribute. Since they did contribute on those terms, we have no reason to think they want to be paid.

https://github.com/influxdata/influxdb/blob/master/LICENSE

Even if he contributed, I think it's likely that InfluxDB helped they contributor more than he helped InfluxDB.

For every woman on github there are 18.3 men. So yes, "he" way way more likely.