When you say "friendlier" does that also mean "less powerful"? Prolog's execution engine is very capable, so does Nova give up some of that power in exchange for friendliness or does it somehow retain it?

Depends on what you mean by power, I suppose. Nova is Turing complete, so there's that.

One big difference between Nova and -most- logic languages is that "forgetting" things is a normal part of operation. Nova is also forward chaining, rather than backtracking.

The end result ends up with Nova programs being something closer to an interpreter in a lot of cases, and writing inputs for said interpreter.

So, Nova doesn't do as much on your behalf as Prolog does, deliberately trying to be easier to reason about, and to have more predictable performance characteristics.