No! You only need one MoneyWiz Premium subscription to use MoneyWiz on all available platforms (iOS, Mac, Windows and Android).
Make sure to create a SYNCbits account for cloud sync, from the device where you bought the subscription. Then log in with the same SYNCbits account on all other devices. The subscription will sync to all devices via SYNCbits and MoneyWiz will recognize that and unlock itself, so you don't have to purchase more than one subscription.