As a programmer do you earn your living from a non-regular job?

Non-regular job means anything that is not a 9 to 5 kind of job where you are an employee of an organization. It can be anything else other than that. Although I am more interested in something that generates a livelihood for you but is low maintenance.

For example: Maybe an app that you update or solve issues for seldomly but it generates income. Or maybe a library you wrote that is open source for individuals but has a corporate license and Patreon kind of donations.

If you are someone like that, can you share your "means" of livelihood and if it is not much trouble how and when it started and where it is now both feature wise and income wise?