Battle Royale mode is a variant on WUAS that focuses more on the player-vs-player mechanic rather than the gold coin collection.
Rather than collecting coins, the goal of WUAS: Battle Royale is to be the last player standing. Every player starts with a certain number of lives, depending on the number of players in the game, and when you run out of lives, you're out. Game over. Additionally, once the first person dies, signups are closed.
Wishing is also a bit different. Everybody starts with a set number of gold coins (again, depending on the number of players). Making wishes costs coins. A wish costs one coin, by default. Every time someone makes a wish, the cost of the next wish goes up by one. If a full turn passes with no wishes, the cost resets back down to one. The wishing restrictions are otherwise the same.
If you are responsible for killing someone, you get to steal one item or gold coin off their person before they despawn.
Finally, if you are finally eliminated from the game, you get access to the ghost chat, where all of the dead players can chat freely. Additionaly, you can choose to haunt a particular space, which secretly corrupts its effect. Once someone lands on the haunted space, they trip its effect, and you can move to a new space. Obviously, you can't haunt protected spaces, like Start or the Altar. Once you're dead, you can't win the game, but you can get revenge on the player who did you in.