No additional purchase is required.
Esri requires that when you use ArcGIS basemaps, ArcGIS data services, or ArcGIS API technology in your app you must also include Esri attribution. There are specific requirements for attribution you may be required to address in your app depending on how your app is built and the data it uses.
- Data attribution (basemaps, data layers), when you use specific data hosted by ArcGIS location services that require attribution.
- Esri attribution, using Powered by Esri, when your app is built with Esri API technology or uses ArcGIS location services.
More information on attribution requirements can be found on the Attribution in your app page.