The main goal of Callisto is to research and develop a reference implementation of a self-sustaining, self-governed, self-funded blockchain ecosystem and development environment. Callisto aims to establish a secure and contribution-friendly environment for further protocol development and improvements. It will rely on a built-in system of smart-contracts to achieve this goal.
Decred aims to build a community-directed digital currency whose security, adaptability, and sustainability make it a superior long-term store of value. It is achieving this aim by building the world's first truly decentralized autonomous organization.