When the player asks him for woad leaves they will have a two choices about how much to pay. Buying one leaf for 20 coins is the best option as it results in him giving another one free as a reward for the player having been a "generous" person.
The player will receive only one leaf if they choose to pay 15 coins
Although Wyson is friendly and even helps the player, he will attack them if caught digging in the park at the end of the Pirate's treasure quest. There is no consequence for killing him, and he will respawn. The fight with Wyson can be avoided by having another player lock him in dialogue by talking to him before the other digs for the treasure.