> I've often dreamed of a system where normal users, give money as a promotion for a certain issue to be fixed or even created

It might be good to have such a system as an option, but I wouldn't want it to become an expectation. I've got a couple of side projects that are out on GitHub. They have open source licenses and anyone is welcome to fork them, send bug reports, or pull requests, but I don't want to have any obligation of supporting those projects.