The Advent of Code https://adventofcode.com/ is a yearly code challenge that has a variety of practice programming problems. Because the website has ads to pay for hosting, its creator, Eric Wastl, writes all of the programming problems himself. His website, despite being freely available to all, is commercial. He specifically refuses to accept or even look at problem submissions to avoid copyright issues.
Similarly, I may use the Programmed Patterns code in a similar way in the future. Therefore, all contributors must agree to turn over copyright of their contributions to Al Sweigart.
This code repo is freely available on GitHub, however for IP reasons it is copyright Al Sweigart.
I plan to keep this repo and the ProgrammedProblems module freely available, but I also plan on using these programming exercises in a commercial book project. I plan on charging the minimum 99 cent price for ebooks on online retailers, while also making the ebook freely availble on inventwithpython.com. The commercial aspect does mean that I need to be the copyright holder for all content though.