Location is necessary, but GPS is not, and you will have to choose the first 2 kinds of Location Mode: High accuracy or Battery saving.
LunaR asks for mobile network to access location, not GPS, so you will have to have a SIM card in your phone.
To use LunaR Android App, "Location access" must be turned on. There are 3 location mode: "Device only" requires GPS; "Battery saving" requires WLAN and mobile network; "High accuracy" requires GPS, WLAN and mobile network. With more requires, the location will be more accurate. LunaR requires location to use all the smart features, like second time zone and sunset&sunrise, but it doesn't need the highest accuracy and GPS consumes so much battery, so GPS is not a necessity.