WiFi Only iPads
WiFi-only iPads are not supported by MilGPS because they do not have a GPS receiver in them.
They are capable of determining their location via nearby WiFi networks but this is less accurate and has highly variable coverage. WiFi+Cellular iPads have a GPS receiver in them and are fully supported by MilGPS.
Some users want to use MilGPS on their WiFi-only iPad for planning purposes, where the reduced location accuracy wouldn't matter. Unfortunately there is no way of allowing this reasonable use without also allowing new users to buy the app on their WiFi-only iPad, with resulting poor user experience and support inquiries.