FoundationDB is an open-source transactional KV store where you can write to any replica, and continue writing even if a certain number of replicas are lost. The transactions maintain strict serializable semantics, meaning that transactions happening at the same time against different nodes will be consistent. (You can't read bank account A's balance, add to it, and then write it back if someone else committed a change to the bank account balance, even if that happened on another node.) This is honestly a pretty rare property in distributed databases, and even in databases that claim to implement it, it is ridiculously easy to get wrong. (Reading the analyses here are fascinating: https://jepsen.io/)

One of the many things that SQLite brings is the ability to treat arbitrary storage as a relational database that can be queried (and mutated) with SQL.

Both of these things are generally rare in open source databases. There are very few multi-master distributed databases that have ACID transactions, and even fewer of them have SQL support. So marrying these two technologies is extremely compelling; you get the power of SQLite's relational data layer with the power of FoundationDB's distributed transactions. This is really high tech stuff for free!

A different implementation of similar semantics is rqlite. rqlite uses the Raft consensus protocol to replicate the text of your database writes to each node, which commits it to a local on-disk sqlite database. I haven't actually looked at mvSQLite enough to know how different the approach is, but both should be on everyone's list to take a look at and poke at. (For most "work" you'll be doing, it's probably completely fine to not create a distributed system like these; run in one datacenter, run a monolithic RDBMS, and tell users you're down when a tornado flattens the server racks. Do keep some offsite backups either way, though. Your application code will always have bugs, and these databases will happily replicate an accidental delete to 5 data centers at the speed of light.)