Open Source creates a big ecosystem, a soil where different "plants" grow and revenue. And as in any ecosystem beings have to contribute to it. Streightforward it is or not but if Open Source didn't exist the productivity and popularity of different solutions we bring to our customers wouldn't be so amaising and appealing.

We get effective solutions at no cost, we save our time and nerves, we get more customers willing to get some "it toys", we grow, our communities grow and we have time to contribute. And because of the greater community people who make contribution as their full-time job can get enough money from that. Enough at least to make them continue at what they are doing. Examples are Spring, Hibernate etc.

They do it not because they got insane and forgot to charge for their software but because they really think that the wider their software is spreaded the more money they get from "indirect incomes". Just think about the duration of the Open Source Initiative. If it were not profitable it would have already died. But it doesn't look quite dead, I think.