To transfer your backup license please visit the control panel and click on 'Account' and then 'Health Check' here you will be able to un-assign and re-assign licenses to any one of your devices.
You only need licenses for backup. The app can be installed on any number of your computers and you can still use the sync folder and restore files without a license.
Mobile devices such as iPhones, iPads and Android Cell Phones do not require licenses in order to be backed up.