You can use the OpenStreetMap data, more info can be found on the wiki https://wiki.osmfoundation.org/wiki/Licence/Licence_and_Legal_FAQ (very brief summary you have to include (C) OpenStreetMap Contributors on any map you produce and any additional data you add will have to be released as ODbL as well)

You will have to ask the healthsite.io team whether you can use any of the maps they produce or other data that is used.