Thanks! Unfortunately I haven't done much with it in a while, just enough to keep it running on modern linux systems, but it still works nicely. (code is here: https://github.com/mempko/firestr)

Data lives on the clients. How multi-writer is handled is up to the app you write but I have built in support for vector clocks. So for example, the built-in app editor uses vector clocks and a merge algorithm.

I thought about adding CRDTs for making syncing data structures easier. Maybe there is someone out there that is motivated...