You could go the Grayjay approach and have it be "paid" software but not stop you from using it without pay, not even anything other than a small buy button which stays until you pay.

[–] MudMan@kbin.social 3 points 9 months ago

That is most likely going to generate less revenue than promoting donations, or a comparable amount at best. WinRAR is the meme example.

From a PR and marketing perspective, if I wanted to maximize my revenue as a single developer I would set up a Patreon or encourage recurring donations through the software by providing bragging rights stuff (merch, insider access, early access to unfinished builds and so on). Single mandatory payments simply reproduce the piracy/license access of commercial software and shaming people into paying without coercion just makes you seem less appealing to people who would donate anyway.