Folk musician Johnathan Coulton had taken to Twitter earlier in the week to express how he felt about Glees use of his cover. Glee “ripped off my cover of Baby Got Back”. If you listen to both covers it’s clear that a lot of the ideas used in the Glee version are brought in from Johnathan Coultons original cover.
Even though the Glee cover is almost identical to Johnathan Coultons, there are no copyright laws that allow him to make any claim from others covering his cover. His arragement with the original recording studio allows him to sell his version whilst they retain all copyright for the lyrics, which is why the Glee production team had no need to inform him about the heavy influence of his cover.
Johnathan Coulton does however seek acknowledgement for his effforts in reworking the song rather than money. Which is certainly deserved even though the copyright system doesn’t rectify it.