How about Boscoin's Modified Federated Byzantine Agreement? Does anyone know how it relates to POS? I was not able to understand it.
Federated consensus decouples trust from resource ownership and requires no assumptions about the rational behavior of attackers. Boscoin's consensus protocol is "modified" from Stellar's in that nodes form clusters and validate with their close peers first; it's faster but there's still the problem that there's only one central blockchain - all validations have to propagate eventually to all nodes.