Was curious what was being used for geocoding, but it is just a hard-coded list of ~40 cities with their lat/longs.
These seem to be the most generous (free) geocoding api's
Forward geocoding (location name to lat/long)
- Open Meteo 10,000/day: https://open-meteo.com/en/docs/geocoding-api
Reverse geocoding (lat/long to location name)
- OpenWeatherMap 1,000,000/month: https://openweathermap.org/api/geocoding-api
- Also has forward geocoding; seems more comprehensive than Open Meteo DB.