mysql5 profile is only used for testing - it has no influence on packaging, and does not install any additional libraries into packaged GateIn.
In order to use GateIn on JBoss AS7 with MySQL you have to install MySQL JDBC driver yourself, and adjust current datasource configuration in JBOSS_HOME/standalone/configuration/standalone.xml to use mysql driver.
OK. I was lead to believe it held magical powers by the top level README in git that says:
2) Database configuration
By default the build uses a HSQLDB database. However, it is possible to use MySQL5 by using the 'mysql5' profile.
Perhaps that file should be updated.
Thanks for the info!