ANY hit is considered to have caused damage. Hits to the torso are death, hits to arms or legs render them useless. Javelins are well padded, light-weight spears that may also be used for throwing. Javelins may be picked up and thrown by anyone, but cannot be carried around or used as thrusting spears except by their owner. Thrown, javelins pierce all armor except helms and do damage the same as arrows.
White weapons are chunks of left over foam that have been covered in white fabric.
No, you can't add metal weights to make them heavier. A hit from a white weapon to the head is death, no damage is done from a hit anyplace else. You may block whites in any manner, except with your head. Anyone may pick up and carry white weapons with them. A white weapon MUST be dropped or thrown in order for it to count, they cannot be used as hand weapons.