Seekers Notes is entirely free to download and play.
However, it also offers "in-app purchases." These purchases are never required to play the game, but can be used to enhance certain aspects of gameplay.

You can easily manage the ability to make in-app purchases, adjust password protection settings, or disable in-app purchases entirely through your mobile device's general settings. How to do this depends on your device.

Here are the instructions you might need:
Apple support:
Google support:
Amazon support:
Windows support: