Sorry if this sounds harsh but this looks similar to commercial weather services in terms of the types of layers. How does this actually work? Did you manage to track down their other services’ providers and negotiate access?
They can just use the free government services. Most of the 3rd party services just wrap the various government services behind an API.
This is true for many free weather APIs out there. But our weather API is global so we’re not just passing through a single government feed. There’s quite a bit of engineering to normalize all of the data sources. Japanese alerts for example are just XML feeds. All the sources update on different schedules, and have different forecast ranges, so it's a challenge to make sure the best forecast is returned at request time.
Some of our data is proprietary. The lightning strike data is from our own lighting detection network. We also offer the only hail forecast model available which was developed in house :)