Holochain

Holochain is a framework for building fully decentralized, peer-to-peer apps. In its architecture, Holochain leans away from the severely limiting and often destructive consensus-based and data-centric practices made popular by blockchain technologies. Holochain is unique in that it utilizes DHTs for collective data storage and proliferation while maintaining agent-centric data integrity via personal hash chains held by each node.

Holochain is not a blockchain. On a blockchain, every node on a network maintains the same state of the entire network. On Holochain, each node maintains its own history in a personal, cryptographically tamper-proof chain.
DHTs (Distributed Hash Tables) are implemented on Holochain to create shared public space. Each node carries some of the shared data so that if a node goes offline, its data isn't lost to the community. This is configurable for each app's use-case.
Distributed validation built in to Holochain means that every user of an app agrees to that app's validation rules. If these rules are broken, other nodes can tell how and by whom, and then react accordingly.
Each Holochain app is its own network.

Holochains don't manage consensus, at least not about some absolute perspective on data or sequence of events. They manage distributed data integrity. Holochains do rely on consensus about the validation rules (DNA) which define that integrity, but so does every blockchain or blockchain alternative (e.g. Bitcoin Core). If you have different validation rules, you're not on the same chain. These validation rules establish the "data physics," and then applications are built on that foundation.

Each source chain for each person/agent/participant in a Holochain preserves the immutable data integrity and order of events of that agent's actions from their vantage point. As data is published from a source chain to the validating DHT, then other agents sign their validation, per the shared "physics" encoded into the DNA of that Holochain.

The minor exception to the singular vantage point of each chain, is the case when a multi-party transaction is signed to each party's chain. That is an act of consensus -- but consensus on a very small scale -- just between the parties involved in the transaction. Each party signs the exact same transaction to with links to each of their previous chain entries. Luckily, it's pretty easy to reach consensus between 2 or 3 parties. In fact, that is already why they're doing a transaction together, because they all agree to it.

Holochains do sign every change of data and timestamp (without a universal time synchronization solution), This provides ample foundation for most applications which need solid data integrity for shared data in a fully distributed multi-agent system. Surely, there will be people who will build consensus algorithms on top of foundation (maybe like rounds, witnesses, supermajorities of Swirld),