MariaDB is one of several MySQL forks that occurred after Oracle bought Sun.
If this is for an established Xenforo installation you may want to create a backup of your database. I've found moving from MySQL to MariaDB raw on a major installation to be a somewhat tricky process.
I don't remember much, it was while upgrading my slave server to the new Debian testing distribution, so it was one of several different headaches. I have a lot of custom configurations, including paths, so AppArmor naturally blew up, and that's most of what I had to fight with and all of what I remember.