I would like to understand if using the flutter_map package with tile url https://tile.openstreetmap.org/{z}/{x}/{y}.png represents a correct and legal way to implement openstreetmap maps and if so, which rules I have to respect to use openstreetmap correctly, i.e. without violating the terms of use of openstreetmap.
I am a maintainer of 'flutter_map'.
As a mapping library, we can display any CARTO raster slippy map, including OSM.
This a perfectly 'legal' OK way to display any map - if it is public (or private with access granted), and if you are using the tile server in compliance with their ToS. For example, we can also display Mapbox and Thunderforest maps, as long as you follow their rules.
In summary, as stated in multiple places in the documentation, it is your responsibility to ensure that you are using the tile server in compliance with their ToS. OSM cannot restrict our library (and we are not responsible for your usage) - but they can restrict you.
