Basically you pledge bitcoins on a ticket/issue that you want to be fixed or implemented. And the person that does the job collects bitcoins.
I love the idea, and I think it is much better idea than any kind of fund
Also the gittip.com founder has been interested about integrating bitcoin with their system. It is open source project, so anyone can participate.
https://github.com/whit537/www.gittip.com/issues/14
Personally I like the fundhub-model more, but the process has to be very smooth/fluid so that people can start using it. And it should allow "passive" donations - eg. I can give bitcoins to someone who doesn't even have any knowledge about bitcoins, just a github account. Then he/she could easily redeem the bitcoins via fundhub.org