It doesn't really matter, as no one building a product today would use any portion of the original 6510 design that is subject to intellectual property protection. The DTV 64-in-a-joystick, for instance, uses a new 6510-compatible HDL implementation. AFAIK, the only part of the original 6510 design that would be subject to intellectual property protection now would be the actual mask designs, which might (or might not) be copyrighted. No one in their right mind would try to make new 3 micron NMOS processors today, and the mask designs are not relevant to new redesigns.