How can we provide security mechanism for the BB app. There may be ways with I can transfer downloaded JAD/JAR from one device to another device. Which are the ways to prevent JAD/JAR from unauthorized distribution(from User to User).
By default, it is quite simple for a user to transfer an application from one device to another. The JavaLoader utility (which is bundled with the JDE) allows you to transfer any BlackBerry app from your PC to your smartphone and vice-versa. (You might need to be a little bit of an advanced user to do it, but very little.)
One thing you can do is generate a license key that is mapped to the PIN number of the device (or possibly to some other identifying credential such as the user's email address). You can have the app check at startup that the device's PIN is correct, but you have to implement this check yourself in your application. (I've written some sample code demonstrating how to do it in Chapter 5.)
BlackBerry App World has some infrastructure in place to sell the license keys based on user/device identity.