The Bronze 3rd Freeport Games Cape is an award for competing in the 3rd Freeport Games (FPG) and getting third place in a category. It is only obtainable in the games, or from trading from another player, as RAGiNGBiZQUiT did in the photo.
It is unknown if these are exclusive for the 3rd Freeport Games, or if they were awards for previous games as well. It is also assumed their are Gold and Silver capes aswell.