Agento is very much alpha software and no formal release have been made yet. But .deb packages for Upstart-based Ubuntu distributions is build from time to time.
Client package:
agento-client_0.0-20150812-0830-3de046b_amd64.deb
Server package:
agento-server_0.0-20150812-0830-3de046b_amd64.deb
Unified client/server package:
agento_0.0-20151217-2345-a6ef69a_amd64.deb
Source is available on Github.