Does anyone know why we are able to hear a clip of Willie Nelson's song in the Obscene Phone Call episode? Is this even a copyright infringement? Is it because it was under 3 seconds?

On my DVD of that episode they replaced Willie Nelson's "On The Road Again" with some generic country song, and took out Sonya's "He's probably not into Willie Nelson" line afterwards.

They really ought to change the copyright law so 'clips' can be used. Then you wouldn't have silly problems like not being able to use 4 seconds of Willie Nelson.