Install on second device

[empezza]

I tried GoneMAD on my phone, loved it, and purchased the unlocker.
I now want to install GMMP on the Android radio/media player in my car.  When I go into Google Play Store only the unlocker appears - no trial version, and says PURCHASED.
I then click on INSTALL and it proceeds to install the unlocker, then says GoneMAD not installed - download the trial.
Click to download.
Then says "Your device isn't compatible with this version."

The device in the car is running Android 4.2.2

Do I need to purchase a second licence for the app in the car?   How do I do that?

[empezza]

Ignore above.
I found how to copy apps from one Android device to another.
All OK now.

[GoneMAD]

The unlocker is tied to your google account. You only have to buy it once