Woah, I wasn't expecting this kind of huge negative response, I'm sorry for sharing a technique which can generate loads of great new source material! :P
It's not strictly plagiarism, as the technique allows a huge amount of room for personal expression. Often the inverted melody will provide a guide, but signficant modications have to be made to it in order to fit in with the rest of the piece. This is well illustrated with my "Reflections" pieces, which contain a significant amount of my own work, combined with inversions of Beatles melodies.
What's wrong with using other melodies as source material for inversion anyway, or as a guide for a whole set of pieces for that matter? Is Vaughan Williams a plagiarist because he "stole" a theme by Thomas Tallis and the tune "Dives and Lazarus"? Is Bach a plagiarist because he "stole" several tunes for the Goldberg Variations quodlibet? Is Rachmaninoff a plagiarist for "stealing" the Paganini theme?
You would have thought that famous classical pieces such as Clair de Lune, The Lark Ascending, La fille aux cheveux de lin, Rachmaninoff's 2nd piano concerto, etc would have surfaced in their inverted form in other pieces since they were written, but I've yet to discover any (inversions of those pieces appear in my works Cambric Clouds and Egyptian Concerto, Part 2 respectively).
Again, I'm not claiming that I invented inversion or combining melodies from different sources, but I've yet to see evidence of both techniques ever been done before together (and certainly not on a grand scale). I've had positive comments from over 250,000 people on Facebook, and the real magic is that hardly any of them know (or need to know) how the pieces were composed, it just produces great music.
Quit the sarcasm and open your mind to a huge resource of new ideas.