Apache CouchDB, commonly referred to as CouchDB, is a free and open source document-oriented database written in the Erlang programming language. It is designed for local replication and to scale vertically along a wide range of devices.

Overview

If languages are defined by standards, what makes them open source? Well, the specification itself can be proprietary. You'll find in older main frame languages if you wanted the specifications you had to pay huge amounts of money for the detailed specifications.

The second opportunity is the implementation itself. For example with Ruby, there are several implementations, all of them happen to be open source.

Joe Armstrong, a Swedish software engineer, notable as the designer and implementer of Erlang programming language and the chief software architect of the project responsible the Erlang OTP system.
He received his PhD in computer science from the Royal Institute of Technology in Stockholm, Sweden and currently works for Ericsson AB where Erlang was born

(From wikipedia, November 2, 2008)