Thanks Cyrille!
I guess bountysource is easier because the fund is automatically distributed among issue solvers. There's the option to funnel the "bounty" back into another issue once you earned the bounty. But, in the end it is more expensive when you "cash out".
Pledgie sounds great. As far as i can tell you need someone to handle how the fund is split among devs once the upgrade is finished or most issues solved. Since it is very easy to see who contributed to the issues, i also think it is better to use and less expensive. It uses Paypal, and I don't see any objections to this.
Just a note on the campaign type: With pledgie it appears you can do two campaign types, 'everything helps' and 'all or nothing', i think the former is better in this case. Since pledgie uses Paypal, when using the latter type the donation is not withdrawn from the donor until the deadline (if the goal was met/surpassed). By then, if the donor's paypal acount changed, then you might not get the entire amount.
And yes, i will also contribute too as much as i can, cause Gem really excellent code and i learn a lot from it!
fdch.github.io/tv