Which permissions does Dumpster require, and for what purposes?

Dumpster uses the following permissions:

• WRITE_EXTERNAL_STORAGE
  For accessing the device storage
• RECEIVE_BOOT_COMPLETED
  For Dumpster to automatically start after system has finished booting
• WAKE_LOCK
  For restoring activity when the screen is off
• INTERNET + ACCESS_WIFI_STATE + ACCESS_NETWORK_STATE
  For Ads, purchasing our premium offer and using the cloud service
• WRITE_SETTINGS
  For in-app billing purposes only
• BILLING
  For Google Play in-app billing purposes only
• GET_ACCOUNTS
  For cloud account registration