A MoPub developer is responsible for integrating and managing the MoPub advertising platform within mobile applications. They work with the MoPub SDK to enable app monetization through in-app advertisements. Their tasks include setting up ad placements, managing ad inventories, optimizing ad performance, and troubleshooting any issues. They also analyze ad data to track revenue and performance. Additionally, they ensure the seamless integration of the platform to enhance user experience, while complying with privacy regulations. They liaise between the app development team and advertisers, and keep up with the latest trends in mobile advertising.