This is a great concept. I hope it catches on.
I participate in a pledge called #50forFOSS. On the first Friday of every month, I choose an open source project and give the maintainer $50, no strings attached. It lets me target small projects that may not have a lot of users, but are valuable to me, as well as bigger ones with more expenses. My mindset these days is that I need to insist on paying for the software I use, because if I don’t, someone else will (i.e. advertisers and venture capitalists, which is bad) or no one else will (i.e. abandonware, which is worse).
Disclaimer: I started #50forFOSS and there’s a very small group of us who are doing it.
“If you knew what it was, you’d be using it already.”