You can always open a bounty on Bountysource or just offer a bribe if you want some feature implemented. But mostly things that work for Spring and ZK tend to have to either be done directly by people already involved, or by people closely managed by those who know the ins and outs. The problem with bribing those
people is that they're mostly already overextended and their time supply is inelastic.
There are some cases where this doesn't apply. I think it's possible to use outsider modellers quite successfully, for one thing.