The developer portal at
https://developer.nutiteq.com mentions OpenStreetMap, but the start and product pages doesn't. No link either. Perhaps you provide more sources, I haven't looked into the product very carefully. Your support told me OSM is used as map data source, didn't mention any other source. My understanding of the OSM license agreement is that you have to make it more explicit. But I'm no lawyer.
"Our requested attribution is "© OpenStreetMap contributors".
You must also make it clear that the data is available under the Open Database Licence. This can be achieved by providing a "License" or "Terms" link which links to www.openstreetmap.org/copyright or www.opendatacommons.org/licenses/odbl."
Regardless whether required or not I think it'd be cool of you to mention it more explicitly since you're creating a business around it.