There's Bountysource. Dunno if that's what you had in mind, but it seems like a similar principle. People put "bounties" on features in open source projects. So

There's Bountysource. Dunno if that's what you had in mind, but it seems like a similar principle. People put "bounties" on features in open source projects. Someone closes a PR for that feature, they get the bounty. Someone wants to encourage work on a feature, they contribute to the feature's bounty. In my view this is a natural next step for open source as it closes the loop on users who don't contribute code but do use the software. Now they can contribute financially, in theory fueling more code contributors (in practice, most bounties I've seen are not worth the work, but I've only had my eye on one obscure little open source game, so this may not be representative). I think Kickstarter is not great for this model simply because it has a fixed end date for fundraising and there is less of a direct tie to specific features in a particular codebase.