Stealthcoin (XST) has been rebranded to Stealth (XST): https://twitter.com/stealthsend/status/993226001101545473 Stealthcoin provides a complete anonymity solution for cryptocurrencies. Stealthcoin has a fair distribution with nearly four hours of low block rewards, a small premine of 1%, and the long-term energy efficiency of proof-of-stake minting.
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.