I don't see how you could make a "mock" programming language implementation. Either it's a complete implementation, in which case it's just as real as any other implementation, or it isn't, in which case it's an implementation of another language.

Incidentally, the reason we didn't make our implementation too Mzscheme-specific is that we wanted to make it portable across Scheme versions. In fact, it started out written on another version of Scheme, Scheme48.

I believe my rationale at the time was that my implementation would probably be imperfect in some way wrt the de facto standard of the reference implementation, so I didn't want to presumptuously call it "Arc."

And also, every project should have a cute name. My only regret is that I didn't have a logo design contest and print up T-shirts.

The language he implemented is "Mock Arc" - an imitation of Arc. From the project home page:

I decided to call my implementation Morc, as in "mock Arc," as in an imitation Arc.

Why did you decide to switch?

It was so long ago I'm not really sure, but I remember that Scheme48 was not very programmer friendly.

The project's home page: http://www.neilvandyke.org/morc/