What about it? Coulton did an arrangement of Sir Mix-a-Lot's [i]Baby Got Back[/i]. Glee ripped off Coulton's arrangement with no compensation to Coulton, which was licensed under Creative Commons [for non-commercial use]

Coulton would have needed Sir Mixalots permission to cover his song, just as Glee [i]should[/i] need Sir Mixalots permission to cover his song. Really I think it comes down to Sir Mixalot, he probably has some rights to sell Coulton version.

Well, a cover and an arrangement are different. To play/sing someone's song on television, as it was written [for profit] is a cover, and requires the expressed consent of the copyright holder [Sir Mix-a-Lot]. To transform an artist's song into a different arrangement, especially when done non-for-profit and under the Creative Commons license [as Coulton did], does not require the expressed consent of the copyright holder [Sir Mix-a-Lot]. What Glee did was take Coulton's arrangement [which Coulton did entirely legally and within copyright law, and released for non-commercial use] and use it without any attribution to Coulton, and they're making money off of it by using it in an episode of Glee and selling it in the iTunes store.