Hello!

My name is Nikolay, I draw OpenStreeMap.

you made an excellent service, but violate the rules of using Openstreetmap

I noticed that you are using tiles with OSM data from mapy.cz.

According to the terms of use of OSM, you must specify a reference to the data source

We demand that you use the credit "© OpenStreetMap contributors".

For a browsable electronic map, the credit should appear in the corner of the map.

see more here
https://www.openstreetmap.org/copyright/en

I hope you stop violating the terms of use of openstreetmap

Nikolay Petrov,
openstreetmap contributor