I actually do not believe it is against ToS as long as it isn't for real money as they are asking for gil most likely.
Below is the only thing in ToS for selling.

2.2 Real Money Trading, Farming and Power-Leveling. You may not sell, purchase or exchange for real-world money or value any in-game currency, accounts, characters, in-game services, or in-game virtual items. You may not play the Game for the purpose of acquiring virtual items or advancement in game play on behalf of a third-party or for the purpose of selling any virtual assets to a third party for real-world money, specifically including "gold-farming" and power-leveling services.