OpenBSD doesn't do this anymore; perhaps they got to the point where it didn't sell enough to make it worth the trouble, since you could download all the same files for free.
Of course, some companies do just donate money for open source, many more donate in kind - e.g. with hosting services - and still others develop internally and donate source code.
Naturally they do this because continued maintenance of the software supports their business objectives, and not out of an egalitarian sense of charity.
You can donate money to a project to hope for help when you encounter some critical bug in the future. However, you don't actually get any guarantees that the community will help with said bug or return your money if they don't. That's a really hard sell if you're trying to pitch it as insurance.
And that's the problem.
I tried to explain that companies and governments (especially governments) just cannot donate money for open-source. In IT, everything has a price and is a line item and needs to be justified. If a company doesn't have to pay that $100 for a badge on a website, they won't.
I think the long-term answer for open-source, especially for frameworks and languages, is through open-source IT certifications.
Being able to pay for some kind of certification would be a boon for everyone. Developers can show case their skills (and get a tax-deduction on their investment), Employers have a standard they can look for when hiring devs, and open-source communities get money based on the popularity of their projects and can show case who is getting certs or hiring based on them - showing the value of their work.
I'd gladly pay $500-1000 for a cert (even one I know I'd easily pass), but have trouble justifying $100 for warm-fuzzy-feelings, even when I know its going to a framework I depend on.