Both distributed databases based on erlang (most of which I guess run on erjang anyway) not distributed systems such as boinc.

The OP is talking about the system part

i.e. Not merely using a distributed system such as erlang, couch/mongodb, and pretending you can do distributed systems.

It's funny that you would pick boinc (a rotten mashup of C and PHP with no formal spec) as your exemplar of a distributed system.

There's Riak Core which is a framework for distributed systems in Erlang.