DB Commander can be used to open the database files and change values to modify game data. Check out the NBA Live 07 subsite for more information on the different attributes and values used in the NBA Live 07 databases.
Any changes you make in DB Commander are saved automatically upon moving to a different cell in the database.
You should be able to continue using it after the trial period has expired, however some of the importing tools will be disabled. You'll still be able to edit values as before.