Is picking up the sword when it's unenchanted still traitorous? Can a player still be killed after dropping the sword, enchanted or not, if it did not damage anyone?
The sword is only diamond when enchanted, there is an extremely clear difference unlike the Rooftop's axe hence the rule stating "1. Carrying the diamond sword is Traitorous." So no, you cannot be killed for carrying the wooden sword.
When you first craft the diamond sword it is wooden, when you enchant it it becomes diamond. They are the same sword but it is only traitorous in diamond form.