See, there's a tiny difference you apparently didn't notice:
Coulton took the lyrics, changed the style, added a tune, changed the speed, basically reworked the thing. That's called a cover, and while it isn't as original as making something up from scratch, it does, at least, require a bit of creativity.
Glee then takes the song and does it exactly the fucking same way down to the speed, chordal progressions and everything, with very, VERY minor additions at best. That's what we in the business call "Ripping someone the fuck off." That doesn't require creativity, all that requires is, well, either being a dick and just doing it without permission, or asking and being nice. That's about the only creative process there - working out if you can theoretically get away with being a stealing ass.
Oh, wait, I'm sorry, you already addressed this, didn't you?
All I'm going to say is: If you're going to sit here and say something along the lines of "These two covers have exactly the same amount of creative effort put into them, even though one of them changed nearly everything bar lyrics and the other just blithely parroted it", I honestly don't even know where to start with you.