Peddle is the core of VirtualC64, a user-friendly Commodore 64 emulator for macOS. Check it out today.
Looking for 16-bit? vAmiga is a Commodore Amiga emulator which is as user-friendly as VirtualC64.
Moira is the virtual CPU driving vAmiga. The CPU core is maintained in a seperata repository and as easy to integrate into your own application as Peddle.