RSK is an open source smart contract platform that is secured by the Bitcoin network. RSK is designed to add value and increase the functionality of the Bitcoin ecosystem by providing smart contracts that are compatible with the network's code and can be written in Solidity. RSK smart contracts are powered by the SmartBitcoin (RBTC) which is linked to Bitcoin. (1 RBTC=1 BTC)
RSK developed the RIF Token which is intended to enable users to access a range of DApps within their ecosystem. In September 2019, RSK purchased the Spanish social media platform Taringa with the goal of using the RIF token as an incentive to encourage users to share content.

Aeternity is a smart contract driven blockchain platform that aims to integrate real world data and improve the overall performance of smart contracts. Aeternity has a hybrid consensus algorithm that combines PoW for verifying transactions, and PoS for governance purposes. The platform is based on a system of state channels that allow users to interact privately with each other and record this information off-chain.

Ubiq is an Ethereum fork that aims to create a more stable smart contract platform for building DApps. Ubiq's protocol currently uses a Proof-of-Work (PoW) consensus mechanism, but will switch to Proof-of-Stake in 2019. The network is powered by the UBQ coin.
Ubiq's goal is to create a reliable and stable platform for developing DApps by modifying Ethereum's code base with important changes that will make it more secure and reduce instability. Consensus is based on their Flux Difficulty Algorithm, which is designed to constantly adjust the hash rate to protect against network attacks.