MariaDB

http://askmonty.org/wiki/index.php/MariaDB

MariaDB is a community developed branch of the MySQL database that uses the Maria engine by default.

What is the goal of MariaDB?

To provide a community developed, stable, and always Free branch of MySQL that is, on the user level, compatible with the main version. We strive for total interoperability with our upstreams and our own community.

MariaDB will be kept up to date with the latest MySQL release from the same branch. For example MariaDB 5.1 will be kept up to date with MySQL 5.1.

http://askmonty.org/wiki/index.php/MariaDB_versus_MySQL