OSM attribution should follow their guidelines for attributing

[tmiosmauli]

OpenStreetMap has quite strict policy for attributing their work - see https://osmfoundation.org/wiki/Licence/Attribution_Guidelines

In Tarmo the license

The issue could be fixed in a number of ways:

• Provide the attribution in the "splash screen" that comes up when opening the web page (it can be hidden so it's not shown in the future - hopefully this is not an issue as all first time visitors will see it and not showing it in the future is a choice not default action)
• Provide the attribution in one of the corners at all times when OSM data is visible on the screen (requires building logic)

[Rikuoja]

IMO, the splash screen is a good place for such information, will just have to see what it looks like combined with all the other information.

Probably good form is also to attribute MML, lipas.fi and Museovirasto for all their data, as they make up most of the map.