Maybe you are so kind and ask them to sign a waiver the waiver as described here https://blog.openstreetmap.org/2017/03/17/use-of-cc-by-data/ or directly as template https://osmfoundation.org/wiki/Licence/Waiver_and_Permission_Templates ? Just so i can be saved on https://wiki.openstreetmap.org/wiki/Contributors so there is no doubt anymore and the question does not arise anymore?