It's neither Prolog nor a "dialect". From the intro:
> Dialog is a domain-specific language for creating interactive fiction. It is heavily inspired by Inform 7 (Graham Nelson et al. 2006) and Prolog (Alain Colmerauer et al. 1972), and substantially different from both.
> Dialog is a domain-specific language for creating interactive fiction. It is heavily inspired by Inform 7 (Graham Nelson et al. 2006) and Prolog (Alain Colmerauer et al. 1972), and substantially different from both.