Downloading PS3 games for free from unofficial sites is piracy—illegal, unsafe (malware/ransomware), and risks console/PSN bans.
If your PS3 is on firmware ≤ 4.82 (or 4.84–4.90 with exploit), you can install HEN (Homebrew ENabler) or CFW (Custom Firmware) to run backups of games you legally own. This requires technical skill, voids warranty (irrelevant now), and carries brick risk. Never pirate.
Support developers: buy used physical or wait for sales. The PS3 library is cheap and vast.