Every piece of art is a collage of other pieces of art. Everyone is inspired by other, and copies others, whether they admit it or not. You can't write a song or paint a picture and say that the way you stroke a brush or strum a guitar is not something that was learned by watching others. I think in general too often people are awarded copyright judgements when they shouldn't be, however in this instance I do feel that absolutely nothing of artistic value is being added, and it does seem to be intended to replace the original. If you like a song you heard, and you write something with the same chords, and a similar melody, that's fair game, but if you write something so similar, _and_ market, and sell it as a replacement "don't buy that expensive song, this ones basically the same, and half the price", then I'm quite sure you're in some very murky, and potentially illegal waters.