It's very difficult to do well is why. * It changes the dynamics of the project when other people see you're making money on it. * Dual licensing might hamper

It's very difficult to do well is why. * It changes the dynamics of the project when other people see you're making money on it. * Dual licensing might hamper adoption. * Service contracts are not easy to work out, and the better your code is, the less likely people are to even need them.