Two teams in the same firm, as gruez says below. The key is that the second team does not look at the internals of the product, and that the two teams communica

Two teams in the same firm, as gruez says below. The key is that the second team does not look at the internals of the product, and that the two teams communicate only by specifications of interfaces (physical, software, electronic, etc.) and not of behavior. This approach to cloning was established long ago (1960's) by IBM's competitors and has always been legal. You can just google "clean room design", Wikipedia is quite informative on it. BTW a few early PC firms did try to cut corners and clone the PC BIOS without the chinese wall; they were sued and died. This isn't theory; it's been practice for decades.