Recognizing the fact that a lot of open source projects are maintained by developers working alone and in their spare time, the idea is to encourage other developers to by specifying a monetary value to a bug report or feature enhancement. Once an initial “Bribe” has been posted others can “chip in” and add to the financial incentive.
Of course, open source means that you are always free to modify the program and even pay a programmer to fix a bug or add a new feature. This is the big point of open source. In this case, however, the idea is to use cash as a sort of voting system for what users really want done and to implement the changes as part of the public codebase.