Social networks are becoming more open, more interconnected, and more distributed. Many of us in the web creation world are embracing and promoting web standards - both client-side and server-side. Microformats, standard apis, and open-source software are key building blocks of these technologies. This model can be described as having three sides/legs/arms/spokes - pick your connection: Information, Identity, and Interaction.
DiSo (dee • zoh) is an umbrella project for a group of open source implementations of these distributed social networking concepts. or as Chris puts it: "to build a social network with its skin inside out".