You have to admit, most open source projects suffer from a lack of funding. I don't like this particular solution but something like it could work. It's supposed to be opt-in for project owners, and that's ok as far as I'm concerned.

As far as the forking issue, nothing really stops zero-effort forks from seeking compensation. Anyone could fork a project and replace all the donation links in the docs with their own. So if you do want to donate to a project, do a little research.