It cannot be with 3.0. Subscriptions and one time charges are only supported for apps that initially cost money. You could get away with charging .99 cents for it initially and then charging a subscription.
You'd have the make the subscription cheaper to offset the app's cost, so you'd still be losing money on piracy. Plus, making the end user pay twice sounds annoying.
It sounds like Apple set it up this way to make sure they are getting a piece of all the money coming through the iPhone. I won't begrudge them that, but I feel for the developers.