The meaning of Free Surf: growing up as a competitive surfer, sometimes surfing was stressful. Battling for waves, hoping the judges scored you well, etc. But then, you would go for a free surf! No judges, no concerns, just you and the waves! Free to ride the wave any way you want.
I imagine music is the closest any non-surfer can get to the feeling surfers call "Stoke." When you are on the dance floor and everyone is interpreting the sound waves with their own dance. No worries of being judged, just moving to their own rhythm.
