The paid version has ads.

It really pis*es me off that you continually downgrade the quality of App that you put forward. I paid for the app years ago. Features have been removed that I am accustomed to, and I am not happy about it. The latest update made me lose my tile tracker, and theres no way to get it back. Im sure you will start charging for it like you do on the computer. But thats not right; it was a feature that I had earned before and now its taken away.

TheFletch about SCRABBLE Premium, v5.15.0