The plausible promise

In “The Cathedral and the bazaar”, Erick Raymond says:

“When you start a community building, what you need to be able to present is a plausible promise. Your program doesn’t have to work particularly well. It can be crude, buggy, incomplete and poorly documented. What it must not fail to do is (a) run, and (b) convince potential co-developers that it can be involved into something really neat in the foreseeable future.”