Wikipedia
UltraESB
UltraESB is a lightweight enterprise service bus (ESB) capable of supporting many transports and message formats natively. It allows messages to be mediated via Java or JSR 223 scripting languages through an API, and is the first ESB to claim support for Zero-Copy proxying of messages with Non-Blocking IO capabilities. In 2013, it was selected as the ESB and API Management platform by a recent Fortune #1 company based on its performance and stability.
The initial version was published in January 2010 and the code was subsequently open sourced under the OSI approved Affero General Public License ( AGPL) in 24th of August 2010. Continuous nightly builds are there to ensure the performance of latest development code.