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.
Neblio (NEBL) is a project that is developing an open source enterprise blockchain solution. This solution will be a secure and distributed platform upon which businesses can develop their own applications. Neblio is joining a long list of other projects such as Ethereum's Enterprise Ethereum Alliance (EEA), Hyperledger Fabric and R3 Corda that are working on similar enterprise blockchain development networks. Check out CoinBureau for the full review of Neblio project.