MariaDB® is based on the MySQL® Server 5.1 code base and offers an interesting alternative to MySQL® in light of the uncertaintity about the long term licensing policy for MySQL.
Both databases are released under the GPL v2 license.
See the MariaDB developers' comparison for more information about the compatibility of MariaDB® and MySQL®.
We have not tested JobScheduler with MariaDB® Server (August 2013) but have tested it with the MariaDB® JDBC connector (version 1.1.3 and newer), see Which Database Management Systems are supported by JobScheduler?
The MariaDB® JDBC connector is released under the LGPL license which allows it to be bundled with JobScheduler. Starting with JobScheduler release 1.5.x the JDBC connector is included with the JobScheduler installer.