For many, the money is not the end goal itself, It's about what you can accomplish with the money. This is a community based on startups, and the founders can identify with this. If they can make a little money on the initial product, they can take it to the next level and serve users better with the money by paying it to others. Make no money and your startup goes to die and no, it's very unlikely that a willing army of hackers will descend on your git if you open source it and make it better for you and others. Instead, you're more likely to get people who are trying to use it for free, and make you feel obligated to support it for them.