I give away my database publishing software (https://www.speedata.de/) for free and make a living with offering services (helping companies producing high quality product catalogs and datasheets etc. using the software) Its not much, but I live a happy live.

I spend about 1/2 of the time doing services and 1/2 hacking on the software. Quite often, customers are paying for new features in the software so it is paid hacking. Great!