I think I have donated more for Inkscape, Gimp, Firefox, and Libre Office than I ever spent on proprietary software. I also tend to buy paid versions of open-source apps in app stores, where available. It's great when a piece of open-source software has an easy donation link / button.

That said, I tend to trust all closed-source software significantly less, even if it's given away for free. Especially is it's given away for free.