It's a neat idea, but whether anyone actually wants this is debatable. Previous attempts to monetize open source contributions have not really taken off either — I think because of the relatively small sums. It feels better to spend a few hours creating a feature and opening a PR by donating your time than to get paid far less than market rate eg $10 for the branch. Also, I'm not sure if adding money to the exchange creates liability for the programmer with no contract in place.