The company I work at employs a few open source devs and we usually hire people who are already doing things we want, but we just want more of, or to have our use case a bit better supported.

We don't really get to dictate what they code,we just pick people who are already, to scratch their own itch, coding what we need.

So yes, there is a lot of paid work, but it's got a very individual character to it compared to my job where theoretically I could be coding anything a customer had convinced sales we needed.