Alot of the queries we received on our helpdesk cover these particular questions.
1. How to Get Application without Paying / Re-Purchasing again.
A: Just log on to Google Play using the email address you used to initially buy the application before.
Play will automatically sync your purchase history and should not charge you again.
Official Play Documentation: http://support.google.com/googleplay/bin/answer.py?hl=en-AU&answer=113410
2. Restoring Add-ons (In-app Purchases/ Premium Maps)
A: Just click on MENU > Purchasing Add-ons > Click on "Restore Purchases" This would re-sync all your premium maps purchase history with Google Play (assuming the Google Account you used to download the PRO app is the same ID you used to Download these premium maps)
3. Transferring Files (The contents of \bcnav) HERE http://support.crittermap.com/entries/23743293-Transferring-files-from-Desktop-to-Device-Vice-Versa