Here's a little info from their FAQ's page:
What is the Dill Pickle Food Co-op? The Dill Pickle is a cooperatively owned and governed neighborhood grocery store that aims to provide sustainable, local, and organic goods at an affordable price in Chicago’ Logan Square neighborhood. A co-op is an independent, democratic organization that is owned, operated, and financed by its members. Grocery stores are a high-value asset to the communities in which they reside. The best way for a community to value and preserve their local grocery market is to own a share in it with their neighbors. Ownership in a grocery co-op offers the chance for the consumer to have a hand on the plow, so to speak. The Dill Pickle Food Co-op carries high-quality, affordable foods because its members are committed to offering them to our community. In addition, being a locally owned and managed store means the co-op attempts to support other locally owned producers in Chicagoland and the Midwestern region.
And don't forget the Dill Pickle is open to non-members too!