Javelins can be thrown multiple times per turn - but you only get one free shooting activation after a move now.
So you can do:
Move + shoot, shoot (fatigue), shoot (fatigue), shoot (fatigue)
What you can't do, but you could before is:
Move + shoot, Move + shoot (fatigue), Move + shoot (fatigue), Move + shoot (fatigue)
Previously charging javelins always got a +1 to hit. Now they don't if the opponent closes ranks; so that gives you the option of negating the javelin bonus as a defender. Of course javelins give no bonus when defending, and javelin armed troops are also not allowed to close ranks themselves (but that's not changed), so now you can weather the attack by closing ranks, then counter-attack in your turn.