Maybe I am mistaken, but was Couchbase not forked by one of the original CouchDB developers, with hot paths of code rewritten in C and employing memcache to increase the speed?

http://www.couchbase.com/couchbase-vs-couchdb

http://damienkatz.net/2012/01/the_future_of_couchdb.html (An announcement from one of the CouchDB -> Couchbase developers)

EDIT: I think I confused blog posts. That is a guy involved in Couchbase, no? I forget who but one of the other CouchDB only devs who worked with him was pissed and wrote a rantish piece. Too tired to find it now.