Callisto is a new Ethereum-based blockchain developed by the Ethereum Commonwealth team - one of Ethereum Classic's dev teams. They have previously brought us ERC223 token standard, ClassicEtherWallet - a wallet for Ethereum Classic tokens, DexNS - a DNS service for Ethereum Classic, among other projects. At Ethereum Classic's block 5,500,000, or roughly around March 2nd, 2018, Ethereum Commonwealth team will snapshot the ETC blockchain, and CLO tokens (the native currency of Callisto blockchain) will be airdropped to the same addresses on the new blockchain. Meaning, if you had 10 ETC at block 5,500,000, you will be awarded 10 CLO when the Callisto launches.
This is a companion discussion topic for the original entry at http://rados.io/what-is-callisto-project/