At the bottom of this site, you will find a small image that says "Open bounties". This image fetches bounty data from the project page on FreedomSponsors which is very much like BountySource, just made specifically for OpenSource projects and they take a much smaller share of bounties.
It works like this: I offer some bounty money, for example on the HDR Resize Bug. Others can pitch in, like Steve pitched in another 5$ to fix that bug. You can press the "Work on this issue" to indicate that you are trying to solve it, and when done you request to receive the money for the work, I verify the work and transfer the money (usually via Paypal). It's very trust-based but I hope we wont have issues with people cheating
If you have an issue that you are eager to get solved, you can post a small bounty on the issue too, to incentivize other people to fix it! You can use the Github issue link to fetch the issue information directly from Github. I recommend everyone to make use of the bounty system! Have fun!