The service agreement outlines the way that services are carried out for clients by the members of a Platform. It defines the responsibilities and constraints by which work is undertaken and is specifically tailored to support the work aspects of the Platform's Shared vision. The shared vision is based on the common elements of all the members Personal visions.
The Service Agreement is written in plain language and is designed to communicate a specific set of concepts to as wide an audience as possible, it's aim is openness and accessibility. A contract for services on the other hand is a legally binding document which is not concerned with readability.