The website you linked explicitly says "Mapy sú majetkom SVP. Je možné ich stiahnuť zadarmo, ale nesmú sa používať na komerčné účely.", which means you can use the map but not for commercial use. OSM data can be later used for any purpose (including commercial), thus it looks like this map cannot be used for OSM.
See https://wiki.osmfoundation.org/wiki/Licence/Licence_Compatibility#Licences_that_forbid_specific_use .