"Freelance software development", problem solved. Not that the tax authority cares at all where the money comes from. They don't have a "cash income" category because they have a deep and burning desire to know these things. They're primarily busy with taking their cut.

It might depend, on country, but I know that usually you can mention donations as "donations" in your income papers/form.

Don't know how it would be for an opensource project. Mentioning something like "open source browser extension uBlock Origin" probably...

Interesting how people report their donations, patreons, etc.

Patreon aren't donations, they are recurring income in exchange of something (membership model with specific rewards per tier). In many jurisductions these must be declared differently.

Patreon sends a 1099-K if you get more than $20K in a year.

https://support.patreon.com/hc/en-us/articles/207099566-Will...