Official: https://bitcointalk.org/index.php?topic=3380156.0

Our team is glad to announce that we’re getting down to the launch of the Callisto coin test network by the developers of Ethereum Classic.
There is a common misconception that Callisto is an ETC fork. But actually, it is an absolutely new blockchain worked out for testing experimental protocols, possible scaling solutions and creating management systems that would have a PoW/PoS Hybrid Algorithm.

Callisto Network is a decentralized, open-source crypto platform based on go-Ethereum source code with its own cryptocurrency (CLO). Introduced by u/Dexeran, the leader of the Ethereum Commonwealth (one of ETC’s 3 development teams), the goal of Callisto is simple: boost the growth and adoption of Ethereum Classic as a community and as a platform.

Mislabeled by some as a hard fork of the ETC chain, Callisto will be a parallel or sidechain that is intended to bring a number of benefits.

A big focus of the project is scaling. Just like any other cryptocurrency, ETC has issues with scalability. Bitcoin was the first canary in the scaling coal mine, and we all know how that turned out (transaction fees and confirmations times have become essentially insurmountable in recent months). ETC devs are tackling this issue via sidechain as opposed to keeping things “on chain” with bigger blocks (like Bitcoin Cash).  

Another problem ETC has faced is that there is no incentive mechanism for holders to retain their coins, a critical feature for a store-of-value token. The introduction of Callisto is a way for ETC to experiment with the “cold staking protocol” which addresses this shortcoming by rewarding holders for being part of the network.

What exactly is cold staking? Cold staking is a smart contract-based process that allows CLO holders to earn interest in a total CLO emission when they hold CLO coin balances for a long enough period time.

Let’s break it down: Anyone who holds CLO can become a cold staker. All that’s required for this to happen is to lock some funds into a treasury smart contract (written in Solidity and deployed on the network) for a minimum period of one month.