As various people have hinted being willing to support SWI-Prolog development financially, I have made an application for the GitHub SWI-Prolog organization to enter the GitHub sponsor program. This has now been approved by GitHub. You find the sponsor page at Sponsor @SWI-Prolog on GitHub Sponsors · GitHub.
All money it will raise will be used to improve SWI-Prolog. My hope is that eventually it raises enough to pay for one or more junior programmers, allowing them to become familiar with the code base, improve it, improve SWI-Prolog support, documentation, tutorial material, etc.
The sponsor options are a more or less random pick from possibilities suggested by GitHub. If you want something else, you are probably not alone. Just inform me, so the options can be adjusted.
Open source is great. Most of us love it. Open source gives the user many more rights. It saves a lot of time and money both for the user and for the developers because all the procedures around it are so much simpler. There is just one tiny issue: it brings in little money for the developers. That is often resolved in one of several ways, e.g., the developer is on the payroll of some company or other stakeholder (mostly my status up to two years ago), the developer is paid through consultancy (currently that is how SWI-Prolog Solution operates), or one or more stakeholders donate to make the development sustainable. This is an attempt at the “more stakeholders” model.