Today, June 27th 2013, Essentia becomes Open Source Software and we start distributing it using the Affero-GPLv3 license (also available under proprietary license upon request).
In the last few months we have been working hard in the code to make a major upgrade of the existing code and we will continue improving it and adding more functionalities. We encourage everyone to use it, test it, contribute to it, and help make it better than what already is. You can find the source code in the github repository: https://github.com/MTG/essentia. There you can find all the documentation, complementary information, and you can download everything.
We have also opened the Gaia library (under the same license terms), which complements Essentia for indexing and similarity computation tasks. It is available at: https://github.com/MTG/gaia.
Over the years many people have contributed to Essentia, but we specially recognize the work of Nicolas Wack, who was its main developer for many years at the MTG and who has always supported the idea of opening it. We have many plans to promote and exploit Essentia. It is a great tool and we all can do big things with it. Please, compile it, use it and give us feedback!!!