PeerLibrary has done a lot of things to welcome new contributors. Our issues are labeled to help new contributors find features that are easier to contribute, a contributor guide, a roadmap with milestones, a development model, and a nice wiki. We promoted PeerLibrary at the Creative Commons Global Summit (Buenos Aires), the Open Knowledge Conference (Geneva), the Mozilla Festival (London), the Science Hack Day (California Academy of Sciences), the Meteor Summer Hackathon (where we were awarded 1st place for highest impact), the Aaron Swartz Memorial Hackathon, the Internet Archive, the Wikimedia Foundation, and Noisebridge. We've received exciting feedback, generous support, and many subscriptions to our newsletter. People we've never met have forked our project. So why don't we have any active contributors beyond our small circle of friends in Berkeley?
We've seen very few contributions from outside our circle. It's hard to make hypotheses with little data, but here are two I can think of:
The formality can be intimidating. We have a lot of contributing guidelines which can be discouraging to a newcomer, especially if perceived as rules. Newcomers are less likely to participate if they think their contributions will be judged against a lot of rules/guidelines or that they'll have to go through a strenuous process of fitting their contributions to a bunch of project-specific standards. If we haven't seen outside contributions, can we afford to be very rigorous with them?
It takes a while to pitch PeerLibrary. The most exciting parts are not obvious. Most of our work so far is not very visible (things like PeerDB, our package that implements database support for reactive references and auto-generated fields). We haven't spent that much time in making shiny features for demos, so our screencast is not as sexy as the project. Our exciting plans for open access (e.g. easy mechanisms to invite authors to make their works available when someone else is denied access) are not that apparent or even documented.
Addressing those issues isn't a trivial task. I think the first one can be mitigated by making our language as welcoming as possible. We should make sure that everyone understands that our guidelines are not rigorous rules. More importantly, newcomers should feel that their contributions will be appreciated no matter what, even if they overlook things. The second issue is more complex. Maybe it won't be a problem once we release an alpha version. Regardless, one thing we can do now is to be more upfront about its role in the open access movement, so advocates can get excited. People shouldn't have to infer why PeerLibrary is important, we should be as transparent as possible with our plans (our statement of principles is a good step in this direction).