Pimmodore is just a «spin-off» of Keymmodore, although Pimmodore being even more popular than Keymmodore itself.

Is a cool way to put a Raspberry Pi inside your Commodore Case, along with your Keymmodore interfase, so I recommend to read about Keymmodore first. If you want to emulate Commodore 8 bits computers with your Pimmodore, the best emulator is BMC64.