I'm wondering along the same path. I can imagine why you wouldn't want to use google as your main source, but any reason you didn't use openstreetmaps apis?
As for the map, I'm not responsible for that matter; but AFAIK it was specifically asked! Besides, every single detail is carefully highlighted manually, so we could say it's more precise than Google Maps (plus the sanctions situation). and as I mentioned in a replay to another comment, KFZ Org. provides local business information; so it basically contains (should contain) every single business and public service available on the island.