Given the risks of "free full" downloads, what are the safe alternatives?

Updating the navigation system requires specific physical media and steps that differ from newer, web-connected infotainment systems. Current Status of RNS 510 Updates

For absolute legality, buy a used V18 DVD from eBay or a forum member. Prices range $20–40.

Requires a tool like the RNS 510 Maps Tool to prepare the SD card and a small "boot CD" to trigger the copy process. VW RNS-510 Firmware and Maps Update - Altechnative