My best friend and I make up Mac parodies all the time - it's great fun, especially after a couple (or 12) ritas.
This commercial used the real lyrics, though - just sung by an off-key chorus of kids. (Sorry - wasn't sure if that was clear or not). Which is funny, considering all the interviews the Mac did when Clinton used it saying how weird that was, since Chris actually wrote the song about/around her and John's divorce. And now it's being used to pimp a homework help website. I know the lyrics are pretty universal, but that's a pretty wide interpretation.