Is there a possibility that you could establish a partnership instead? It sounds like this "someone" simply wants to offer your app as a bonus of sorts to their

Is there a possibility that you could establish a partnership instead? It sounds like this "someone" simply wants to offer your app as a bonus of sorts to their market. You could provide a special free version of your app to their customers, and reap the benefits of those who upgrade to your normal paid version. This path would limit your potential loss of income, keep your code under wraps, and provide you with an incentive to support the free app users (make them happy = profit!). Theres risks and rewards associated with any integration strategy; weigh them out carefully and hopefully that will at least point you in the direction of your magic number