We stand on the shoulders of giants.
This document is a guide to how to pay for your Free Software. A lot of people have put in a lot of time to make your high quality Free Software. They chose to licence it so that you can modify and redistribute it. They often, although not always, gave you the program without requiring that you pay any money for it.
Despite being cheap to obtain the development, testing, and maintenance of the Free Software you use is not negligible in cost, far from it. But unlike proprietary, commercial software, there are ways you can pay for Free Software that aren't money.