If you are a purist, use the Archive as a last resort for lost content, not a replacement for buying the season.
The Internet Archive primarily hosts public domain or CC-licensed content. Most Family Guy episodes remain under copyright by 20th Television Animation / Disney. Uploads of full seasons without permission are technically infringing, though archive.org is a US-registered library and often responds to DMCA takedowns if rights holders complain. family guy season 9 internet archive extra quality