I checked the page and it seems to clearly say "GPS navigation facilities are an optional extra." on the purchase page and reiterates again on the next that "If you want to use SkyDemon while in flight to help with navigation and keep you safe, purchase the navigation upgrade."
Worth noting though that at the moment there is no warning when you try to "Go Flying" in evaluation mode that it will cut out after 30 minutes which is an oversight that will be corrected in the forthcoming update.