Well, the C64 certainly looks the part, but I guess that I am old-fashioned and regard these things the same as custom replica automobiles or motorcycles.

Look nice, very expensive, but not the real thing.

I have nothing against custom modded cases, in fact I think that some of them are very clever, but I do expect them to be original in concept at least.

It's been a long time and I really only got to look at the C64, but it used to ship with something called "GEOS" that looked very much like an Apple OS clone of the day. There may well have been more than one variety of this and in the UK at least, it came with a variety of the BASIC programming language.