I don't think anyone is expecting you to donate to literally every project you use. However, say your business is to build and sell a product done in JS. You already have a bunch of JS devs, whom you may have even bought those sweet MacBooks. Let's also say, you're invested in keeping the code quality high, which you boast about in your product web page. Why not donate a $100/month to the JSLint project which is part of your toolchain anyway and helps you achieve your goals? The annual cost is probably less then you'd spend on the toilet paper for the office. You get a maintained product, they get some money to support their efforts. It's clearly a win win.