The repository has been moved under couchbase account. See it here: github.com/couchbase/couchbase-ruby-model.

Steps to switch the git remote (if you cloned it using this repo):

git remote rm origin
git remote add origin git://github.com/couchbase/couchbase-ruby-model.git
git fetch origin
# optionally reset master to recent version
git checkout -B master origin/master

For users of the ruby gem nothing changed, it still accessible at rubygems.org/gems/couchbase-model.