However, I think it's likely that Fox actually used Coulton's karaoke backing tracks, which would mean Fox infringed Coulton's copyrights. I'm hoping for someone to do a digital analysis showing whether this is true.
He also points to a great example indicating that the beginning was likely edited too: http://imgur.com/a/F0HTP#1
Also, if you're someone that trusts their own ears and has headphones, you can hear Glee's in your left earbud, and Coulton's in your right, in this pairing: https://soundcloud.com/suudo/joco-vs-glee-baby-got-back
Here's why this is an issue. Coulton released his sound recording under the Creative Commons, by-nc-sa . If they used his sound recording, Fox/Glee is infringing all three parts of that license:
- They didn't attribute - They released it commercially - They didn't release it share-alike
A creative commons license is additive, so they could have worked around it by contacting Coulton and getting permission ($$).
Since they did none of that, Coulton has legal grounds here, specifically relating to the use of the sound recording. In my IANAL opinion. :-)