I changed the skin Saturn by myself into showing geolocations with Openstreetmap. (I got crazy when I tried to get an API from Google ...)
Have a look at this URL: https://hartmut.homelinux.org/Diverses/WeiteWelt/index.html
call a map and download the maps.html as well as samapper.js.
Those files are changed. It's a work of a newbie and if someone can workout something better, I would be pleased.
OSM is certainly getting better, but Google Maps is still superior. OSM's coverage is spotty in some places - if there's no crowd, there's no crowdsource. OSM has no satellite, terrain, or street views. OSM rendering is sometimes painfully slow - zooming out or panning around from the initial location can leave you staring at gray boxes for a long time.
I'm sorry this user couldn't figure out how to get a Google Maps API Key. The process is clumsy, but others seem to have been able to navigate it. And unless your site goes viral, it ends up still being free.
So, no reason to switch yet. And I think that if I were going to add an optional, second mapping source, I would look at Mapbox before OSM.
In Saturn, the map is centered horizontally and vertically.
Now grab the lower edge of the browser window and drag it upwards. With your OSM map, you get scrollbars - the map display doesn't respond to the new size of the viewport. Even a CTRL-F5 refresh doesn't fix it.
I'm on a solid, fast connection, but zooming in OSM often produces what you see in gray.png.
As I said, OSM is fine in heavily-populated areas. It gets very sparse elsewhere. Even in my own neighborhood, in the busy northeast corridor of the U.S., OSM is almost useless. Compare the two screenshots - gm.png and osm.png.
I don't like adding things to my skins that don't work very well.
"Now grab the lower edge of the browser window and drag it upwards. With your OSM map, you get scrollbars - the map display doesn't respond to the new size of the viewport. Even a CTRL-F5 refresh doesn't fix it."