General question on usage

Hi, would be helpful if I could get answers to some of my basic question.
I want to use turn-by-turn navigation provided by grasshopper, What is the usage policy? Is it free? Is it paid? I want to implement in my existing project using OpenStreetMap in a flutter app, How can I implement this with my existing project?

Apologies if my questions are irrelevant, I am new to this.

Powered by Discourse