MariaDB now has higher versions 10.0.x and 10.1.
Have moved a Moodle from MySQL to MariaDB before and in reading over the MariaDB info it's called a 'drop in replacement' but that's not entirely true (for the most part it is). Advisable to bookmark/favor links to MariaDB and take the time to read:
https://mariadb.com/kb/en/mariadb/mariadb-vs-mysql-compatibility/
MariaDB folks do highly recommend (which one would do anyway on upgrade of MySQL) to run
mysql_upgrade -u suuperuser -ppasswordforsuperuser
As soon as MariaDB up and running.
There is, of course, Howard's way of importing an SQL dump which suggest that one has made an SQL dump backup of the current DB used for Moodle. When you do, add --events --routines to optons of the SQL dump. STRONGLY RECOMMENDED before you pull the trigger on moving to MariaDB.
Below quote from MariaDB page:
"You should use the --force option of the mysql client when loading mysqldump output as part of a migration from MySQL to MariaDB, and in any other circumstance where system tables might vary between the source and destination."
and
"3. You must run mysql_upgrade after loading an SQL dump from any other version and/or any other software."
Did have an issue with 10.1 MariaDB on a Google Apps Engine instance of CentOS 7 but am not at all sure it was MariaDB ... but rather Google. Affected a Joomla, a WP, and a Moodle 3.1. Chaulking that up to a quirk. On another standalone site, moving to MariaDB 10.0.1 running a Moodle ... no issues.
'spirit of sharing', Ken