It can use openstreetmap as a data source and probably most people self hosting their maps will end up using openstreetmap data and maybe some of their own data

It can use openstreetmap as a data source and probably most people self hosting their maps will end up using openstreetmap data and maybe some of their own data. IMHO this is more interesting for people that want bespoke maps as it gives them a cheap way to do that without having to rely on expensive SAAS solutions or a lot of operational complexity. Openstreetmap doesn't really do a lot for hosting maps for third party websites. You would use Mapbox, maptiler or other suppliers for that and libraries such as mapbox/maplibre, openlayers, leaflet etc. that can render either bitmap or vector maps. The trick with protomaps is that instead of deploying gazillions of tile files, you upload a huge single file with all the vector content inside and then use lambda functions to extract tiles from that file. And then you use caching and CDNs to to make sure you don't have a lot of compute overhead . So, the API looks like a normal tile server. The data deployment process boils down to uploading a new file and your usage data is a little bit of compute for the tiles your users ask for and a networking cost related to using a CDN. So, that adds up to a lot of savings potentially. At least, as long as commercial providers don't lower their cost. Obviously, they are free to do similar things technically.