The App Store policy change reverses a very old rule that banned emulators on the iPhone and iPad.
Specifically, Apple now allows “non-binary software” to run inside apps found in the App Store. The company is specific about what can be launched, with “retro game console emulator apps” included in the list.
Given how existing emulators often rely on user-supplied ROM files, it’s unclear how this will be implemented. In emulators on jailbroken devices, some rely on files to import ROM files and BIOS files, and others have a custom file import feature.
Regardless of the console manufacturer’s stance, the concept of emulation is legal. What isn’t legal is using ROM files the user doesn’t own or the manufacturer’s source code to build an emulator, which is where Connectix’s Playstation emulator fell over two decades ago.