The cpu in the article is real hardware and pin compatible with the 6502, and they use it by putting it into 6502 sockets on old hardware, so no need to emulate the SID chip or anything else--there would be a real one available.
It would be quite easy to modify the design to full 6510, which just has a few more pins dedicated to IO. The biggest issue is properly emulating the bank switching, which they have done for other hardware, but the 6510 has a more complicated scheme.
The C64 bank switching is trivial - the 6510 has a few IO pins mapped to address $1, and a few of them are used for the bank switching.
The bigger problem is that all the RAM is really used for "IO" (in theory anyway) on the C64, as the VICII can remap the character generator (font) location, where it pulls sprites from, and where the screen content is stored.
So a static memory map is insufficient if you want it to just plug into the CPU socket and work.
It would be quite easy to modify the design to full 6510, which just has a few more pins dedicated to IO. The biggest issue is properly emulating the bank switching, which they have done for other hardware, but the 6510 has a more complicated scheme.