Contributors to OSS are giving away their time and energy. That seems to be at the core of open source. I'm not going to demand you pay for what I produce - I'm going to give it to you for free with minimal restrictions in the belief that I will also benefit from others doing the same.
It seems to me that asking how to make money by giving away one's work doesn't really make sense. If you value it highly enough to think you should be paid, then why give the work away for free in the first place. No one picks up trash from the side of the road motivated by cleaning up their community then asks how they can get paid for it after the fact. Either you are motivated to give away your time and energy; or you really want a paid job, but one where you feel like you are giving back to society more meaningfully than just helping a company make more money.