I do not think you can - the way the mobile app is setup you must have already created your account - there is no registration form in the mobile app. My opinion - maybe because the standard boonex app can access any dolphin site, so if you do not know which site as well as have credentials, then it wont know what site you are trying to access. Just imagine the number of spam accounts that would be created on a whole slew of dolphin sites if there was a registration form in the mobile app. That would mean I could create an account on every dolphin based site out there.
If rebranding, I do not know how you could work around this issue.