Talend Installer places the MDM license file into the <JBossPath>/bin directory. When the MDM Server launches for the first time, it looks for a license file in the <JBossPath> and <JBossPath>/bin folders, and loads this license into the database. Next time the server is started, the file is ignored as there is already a license in the database.
If you want to delete your database, note that the MDM server will create another one next time you launch it. Since there is no license file in this new database, the server will load the original license file that is in the <JBossPath>/bin directory.