I'm skeptical that this does anything. I'd wager that just about nobody is sitting around with all this energy waiting to contribute to a project they've never used and just heard about in an HN thread.
I'm sure you get some commitments of people who say they will help. Just like people say they'll pay for your product once you build it and people who say they'll go to an event 6 months from now.
It's hard enough to find contributors among engineers who are using a tool.
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