Social Ledger is an implementation of the new "Proof of Social Network Identity" (PoSNI) consensus algorithm for blockchains. It is based on Harmony (which is in turn based on EthereumJ, the Java implementation of the Ethereum client).
It uses https://github.com/VictorGil/block-validator-using-twitter to interact with the Twitter open Web API.
More information: http://www.devaction.net/2018/05/socialledger-01.html