There are two things that need to happen for a block chain to function:
1) Select the transactions that should be included in the next block
2) Make the transaction history irreversible.
#1 can be accomplished using "consensus" though I am tweaking Ripple's algorithm a bit and calling it Unity.
#2 can be accomplished by using coin days destroyed to make the longest chain irreversible even by the nodes on the Unique Node List
The code will be fully implemented this week for both Unity and Proof of Stake