GADM data version 3.6 is free for academic, educational, and non-commercial use. Commercial use requires a separate license, so ensure your project aligns with these terms before deployment. To help tailor any further GIS steps, please let me know:

Python users can leverage geopandas to read the Shapefile or Geopackage formats:

GADM organizes administrative boundaries into hierarchical levels, denoted from Level 0 to Level 5. Understanding this structure is critical to querying the correct data: National boundaries (Country borders).

Look for the section mentioning older versions or specifically version 3.6.