I'm going to ask a really silly question, how do open source maintainers make a living, compared to the commercial MS Windows world?
Most who make a living out of it work on the project as part of their jobs at larger tech companies or universities. A few manage to start a company around that project and make a living selling various licenses and support. A tiny number manage to (at least temporarily) scrape together a living from donations.
For a large number of them however being an open source maintainer is an unpaid hobby they do on their evenings and weekends.