Are there anything similar to BountySource out there?

What do you want to acomplish ?

If you have a community which may generally support your work with money, you should try your luck with Patreon.com

Otherwise BountySource works quite fine if your project has bugs / feature-wishes which catches peoples interest to throw money on it.

However in both perspectives, you need an audiance. Does that project have that and is the community aware of that ?

Good luck