[dragonwriter]

> Seems like there's another option -- open source your project and also charge for a license to use it.

If you open source your project, unless you're using an unusual definition of open source, you've provided a free-of-charge, sublicensable license to use, modify, and distribute it. (Or, at least, a license that the licensee is free to sublicense without charging the sublicensee or paying an additional fee to you, so even if you are charging for the direct licenses, the more you sell the greater the probability that it will be available at no charge.)

You could open source it and charge a fee for professional support, however, which is a fairly common model.