Most of them would be grateful for a $12 donation.
Why do I use $12 as a benchmark? If you paid a single open source project $1 a month, you could fund their VPS hosting for year by paying $12.
If you paid $24, you could pay their domain lease and VPS hosting as a single benefactor.
Think of some of the most underfunded, most used open source projects you use on a daily basis, and please consider donating what you surely spend less on coffee in a month at least one time a year.
I'm not talking about open source projects that have their own foundation, or limited private company. I'm talking about the random open source contributor whose project you love and use daily who is just an individual. Maybe they don't even get enough attention on GitHub but they're in all honesty publishing something that people (you!) want.
I've published open source projects for 15 years, almost a majority of them now are discontinued or archived, but the ones that are still maintained have been for over a decade. And I have had the opportunity to have my work shared with many people, others are not so fortunate.
It's nearly a full-time job to market them, and mrdoob is right, you end up sacrificing a lot to publish these things.