ESR tries to explain the open source movement with scholarly analysis and categorization. I thought his explanation of different motives was interesting, but he ultimately fails to nail down what makes open source click. My answer: it is in fact magic.
Reading the different takes on how all of these high quality open source projects come about remined me of my economics class. This might be the only thing I took away from micro, perchance. Anyways, we read the essay "I, Pencil," which discusses the miracle of the modern manufacturing industry. We've all seen and used hundreds of No. 2 pencils in our days; the magic is that no one knows how it make it. Every for such a simple product, there is a wealth of factors that must come together to deliver to our worthless hands. Trees, graphite, paint, etc; workers from all over the globe must collaborate to ship, shape, and sell these tiny little objects. In a similar way, I believe that open source is also shaped by the invisible hand. Hard as economists try, no one can fully explain what makes the market tick. I also think it's impossible to pin down exactly why certain open source projects flourish. It's a wonderful thing: through individual efforts of folks from across the globe, software can be created with vast complexity. Although a maintainer certainly has a pretty good idea of how to build their pencil, they certainly can't understand every fork and offshoot that uses their project. When there's demand for products and projects, the invisible hand forms them through the open source community.
Building on the "I, Pencil" essay, it goes on to infer an even greater wonder: everyone involved in the creation of a pencil is working in their own self interests. Most people in the supply chain aren't doing because they want to put pencils in the hands of sad children; instead, they simply doing what's best for them. It's not a perfect match to the open source world, but I think it's similar in that most people who contribute are getting what they want. I'm sure some folks are doing it 100% for the community while not reaping anything in return, but I'd wager the vast majority are doing it because its in their own self-interest. ESR points out this comment:
"You may not work to get reputation, but the reputation is a real payment with consequences if you do the job well."
It's foolish to separate open source contributions from the sense of accomplishment and recognition that they bring. Everyone needs a community. Increasingly, humans are looking online for this sense of belonging. Open source projects are a place where people can chat with like-minded contributors, learn new things for free, and show off their skills. When people act selfishly and stroke their own egos, open source projects blossom.