java supports multiple database via JDBC and further there are numerous ORM abstraction layers like Hibernate and others that automatically handle different database flavors.  

 According to the custom installation documentation, OpenBravo ERP only supports Oracle & PostgreSQL.

 While the OpenBravo POS does in fact support mysql (despite being a java program.)

Database installation

Once Openbravo POS is installed you should decide whether you want to run Openbravo POS on the built-in engine or on any of the other database engines supported. Openbravo POS supports five database engines: Apache Derby, MySQL, PostgreSQL, Oracle and HSQLDB.