Dear the person in charge of TMDB API

Thank you very much for your help in advance. I am a freelancer who develops applications for smartphones. I am currently planning to produce a new smartphone app utilizing the TMDB API. Specifically, when users who have installed the app pass each other, they can exchange information about each other's movies (favorite movies, favorite dramas, etc.) unconsciously. We believe that this can be realized by utilizing the TMDB API and the "passing-by" communication system. Therefore, we would like to ask you to answer the following questions;

Questions (1) Can we use the API free of charge? (2) Are there any restrictions on the use of the API?

Thank you very much for your prompt reply in advance.

Regards, tianlin