Red Hat will switch the default database in its enterprise distribution, RHEL, from MySQL to MariaDB, when version 7 is released. [..]
Once RHEL makes the switch, it will flow on to CentOS, a distribution that provides RHEL without the trademarks, hence making it free in terms of cost.
Read the article at http://www.itwire.com/business-it-news/open-source/60292-red-hat-ditches-mysql-switches-to-mariadb
Related forum thread http://forum.directadmin.com/showthread.php?t=45512