busyba is correct. JoCo licensed "Baby Got Back" under a mechanical compulsory license, which permits rearrangements of the song, so he was OK on that end. However, he got caught unaware when he didn't realize that under a compulsory license, any rights for the song, including any rearrangements made to the song, remain with the original rights holder. Legally, Glee was safe to use JoCo's arrangement. Morally, though, one might have hoped that Glee's musical producers to at least contact JoCo to let him know that they intended to use it. There remains an *extremely* high likelihood that they used his original performance track, one he released on the internet as a karaoke version. There, Glee was definitely in the wrong, as they would have needed to obtain a synchronization license from JoCo, which they did not. However, he opted not to pursue that (rightfully judging 20th's lawyers to be bigger and badder than his lawyers). I believe there also was a reasonable legal argument that, given the original "song" was a rap song with no melody, technically all JoCo licensed under the compulsory license was the words. Therefore, JoCo's melody was a unique creation that he should have owned... but again, that would have required a much more protracted legal fight that he probably would have lost.