Downloading and using legally developed homebrew applications (e.g., retro emulators) is perfectly fine.
The PS3 store was scheduled to shut down in 2021 (Sony walked that back, but the threat remains). When that day finally comes, the only way to install a game you bought ten years ago will be via a backup PKG file. ps3 pkg archive
on the root of your USB drive. The console will automatically use these during the first game launch. Use Package Manager Navigate to Package Manager Install Package Files for USB files or PS3 System Storage if you transferred them via FTP. Select the PKG to begin installation. 4. Advanced Management Tools on the root of your USB drive
The most ethical and legal way to build a PKG archive is by dumping games you already own. This process, known as "dumping," requires either a jailbroken PS3 (running Custom Firmware or HEN) or, for PSN titles, a way to extract both the PKG and its activation license. Select the PKG to begin installation