It looks to me like the Navit car navigation system isn’t meeting OSM’s attribution requirements. The screenshots gallery shows no attribution for OSM, and the Navit :: Planet Extractor extraction tool is using a slippy map with no attribution.
I don’t use it (yet), but it seems they distribute the software without maps, and then you have to download the map from other page.
They can use maps from other sources, like Garmin, so maybe it’s ok that hre gallery shows no attribution.
Maybe the lack of attribution is in the download page, not in the software itself.