Sometimes I miss Facebook for these kinds of things, I wish there was a super popular open-source social network that all my friends would use. Or a free social network without all the nasty practices.
I tried again with a neighboring zip, but this time I hesitated for a moment to make sure I entered it right, and the search box did a weird thing where it popped down an expanded city name along with the zip code. I clicked this and THEN smacked enter, and I got a search results page!
Of course there are no results in my area (and no way to tell how large a radius it considers "my area"; should I try again with a zip a few miles away? a few dozen miles away?), but now I know there's a secret-knock to get into the site.
Yeah, I wouldn't hold my breath.
The OP also talks about "open source", you can launch an off-FB group and tell your friends to advertise it on Facebook.