The open source community has begun to switch from MySQL to MariaDB.
MariaDB is “an enhanced, drop-in replacement for MySQL” and has been created by the developers who originally built MySQL (before it was acquired by Sun Microsystems and Oracle).
The latest major open source project to embrace MariaDB is Wikipedia who announced on April 22, 2013, that they have migrated the English and German Wikipedias to MariaDB 5.5.
Several major Linux repositories have recently adopted MariaDB including Slackware, Arch Linux, and openSUSE.
Update 06/14/2013:
Red Hat has announced it will be switching from MySQL to MariaDB in Red Hat Enterprise Linux (RHEL) 7.