Ducks Unlimited vs Nominatim

Ducks Unlimited publishes a public ArcGIS Feature Service listing its university and collegiate conservation chapters as geocoded point locations across the US and Canada. It's read-only and needs no API key — queryable with the standard Esri REST query syntax (WHERE clauses, field selection, spatial filters) and exportable as JSON, GeoJSON, CSV, KML, and several other GIS formats. The dataset is licensed under Creative Commons Attribution-NonCommercial 4.0, so results can be reused non-commercially with attribution.

Nominatim provides worldwide forward and reverse geocoding built entirely on OpenStreetMap data, needing no API key — only a descriptive User-Agent or Referer header identifying the calling application (the policy states a stock HTTP-library User-Agent will not do). The public instance at nominatim.openstreetmap.org mainly exists to power the search bar on openstreetmap.org and runs on donated servers with very limited capacity: its usage policy caps requests at an absolute maximum of 1 per second, forbids autocomplete-style querying outright, and requires results to be cached on the caller's side. Bulk geocoding is restricted rather than banned — a smaller one-time task is permissible on a single thread and a single machine, with distributed scripts disallowed and anything running longer than a day capped at 4 requests per minute. The policy points larger users first at commercial third-party providers, and the largest at running their own Nominatim instance.