I've been asking myself the same question, another post here suggested that you'll have to provide a method for the user to enter their PIN and license key manually so you can verify them.
I suppose the App World will still hit your server with the correct PIN since it's getting this natively then your app could either incorporate the code to generate a key so you can confirm it or you could query your server with the PIN entered by the user. It will have to be server based anyway because I don't think there is any way to save permanent data via an Android app (like we could with the persistent store on BB OS).
What worries me is the steady flow of users who contact me to say they never received a license key from the App World (from my BB OS apps)..
It's a shame they didn't make the BAR format an encrypted container in which they could embed a key (and from which it would be impossible to extract the APK) the current BAR is just a zip file.
