This is when I admit that the concept isn't quite done baking. My intuitive (read: hand-wavy) answer is that the negotiation between devs / feature requesters

This is when I admit that the concept isn't quite done baking. My intuitive (read: hand-wavy) answer is that the negotiation between devs / feature requesters should take this into account - the pricing reflecting the amount of work * the scarcity of the dev's time. There's also no reason that a single project == a single dev. If it's really an open source project, the feature requests could be posted as bounties and devs could bid on them. Still don't have a solid idea as to how 'contribution timeouts' would work - with kickstarter, the timeline for funding + development + production are all managed by the same party, which simplifies things enough to (mostly) solve this issue. I'm sure that it would have to look different here. All that said, I haven't yet taken a look at the site that someone else responded with, which sounds like it does comparable work. If so, I might just hitch train to them.