Under some jurisdictions (eg Germany), I'm not sure whether the output of a program is copyrightable at all.
Your software, yes, but probably not the output.
What about if the program takes a variety of inputs which influence the output? (At some point there has to be a transition, since e.g. books are "just" the output of some program.)
For any book, there exists some program which generates it, but most books are not created that way (so we consider those books to be products of human creativity).
I was talking about the word processor/text editor, since the things created by them are still just the output of some program (with heavy human influence along the way).
OTOH one could argue that the maze itself does not fall under the scope of the Urheberrechtsgesetz because its threshold of originality is too low (no offense, it is after all auto-generated). But I'm no lawyer and this is just a spooky idea.
I assume it would also depend on whether there were other steps in the process, such as if he selects the mazes for his books, etc., from a larger number of randomly-generated mazes based on aesthetic appeal, difficulty, or other criteria.
That depends on the complexity of possible inputs and the complexity of possible outputs - if your text editor would only allow for single-character documents, I imagine its output might not be copyrightable ;)