When you view a source code of your DNN page, you will notice there is a DNN copyright text has been included by default. In order to turn this option off you will need to login as a host super account. Once login on the site, under the host menu there is a sub menu named Host Settings. Just click this menu and it will load host options page. In the Basic Settings tab, under Appearance section there is an option to include DNN Copyright into the source code. Simply tick this option of and save the settings.