Season 1 & 2 physical are a mixed bag. Some songs retained, many replaced. I never saw the original broadcasts so can’t personally compare, but looking at TuneFind etc, you don’t hear most of the songs listed there.
EDIT: for clarity, s1&2 physical exactly match what’s on streaming. Same mix of original/replaced songs.
ICYMI - Liza Richardson, the music supervisor for FNL talked in a couple of interviews about how they offered artists a 2-year term contract to license their songs for less money, meaning they were original only on the first broadcast:
http://www.fuelfriendsblog.com/2010/08/30/the-musical-mind-behind-friday-night-lights/
And this is exactly why I’m after the NBC captures for the first two seasons