It's all a bit of a licensing nightmare as well, if you want to embed the maps. If you want actual FOSS, you need to be aware of which libraries to avoid (i.e.

It's all a bit of a licensing nightmare as well, if you want to embed the maps. If you want actual FOSS, you need to be aware of which libraries to avoid (i.e. don't touch anything Mapbox with a bargepole anymore - to be honest, their anti-union, anti-open agenda put me off a few years ago regardless of the license change, which is a shame because they used to do really good work).