i would assume they are saying they are not ripping off the movie or the plot, they are ripping off the concept of taking a successful book and making a movie franchise out of it.
potters success was due to the success of the book series.
i mean narnia had a big following but not as big as potter as they were not making the movies as the books were being written.
kind of like star wars or something.
they are making a too vague comparison.