I have played a couple of games in LSS against the c4-c5 line. Both went without any particular issues for Black.
Why is c5 a line? It seems to damage White's queenside structure after Black takes, and preventing White from playing an opposite sides castling game like he usually does in the Saemisch, and it seems Black can take the life out of the position, and get a comfortable endgame.
When I play the Saemisch, most people are dead lost by move 8, and I've lost only 1 or 2 games with it. It really has to be studied if you want to play the KID.