Quoting aitor_czr (aitor_czr@???):

> The substitute for MySQL is MariaDB :)

What you said. ;-> MariaDB is a 100% compatible workalike
(binary drop-in replacement).
https://mariadb.com/kb/en/mariadb/mariadb-vs-mysql-compatibility/

I'm personally also very fond of Drizzle, a cleaned-up, simplified fork:
http://www.drizzle.org/