Sphinx is a software search engine designed with indexing database content in mind. It currently supports MySQL, PostgreSQL, and ODBC-compliant databases as data sources natively. Other data sources can be indexed via pipe in a custom XML format.
Up until version 3, Sphinx is dual licensed; either: GNU General Public License version 2 or proprietary licensing. Since version 3, Sphinx has become proprietary, with a promise to release its source code in the future