The ipsw is downloaded from Apple and later modified. Modification is not illegal just like jailbreaking isn't. Jailbreaking is essentially modifying iOS. Psys

The ipsw is downloaded from Apple and later modified. Modification is not illegal just like jailbreaking isn't. Jailbreaking is essentially modifying iOS. Psystar sold computers with macOS installed, that's redistribution and a copyright violation. Corellium isn't selling devices with iOS.