This person may not have the right to make money off of their work, but if they don't want to give it away, you have no right to TAKE it.
If they choose to offer it up for donations, that's their business. If they want to charge for it, that's also their business. But the moment you want to use their product, you should be bound by their rules.
When you go to buy a phone, do you only pay the cost of materials? Apparently, that's all you think it's worth, since you're arguing that taking the 'bits' doesn't deprive anyone of anything. Well, if you go and get a phone, maybe you should just pay for the cost of the sand that it took to make the silicon and that's it, hmm? That's all that's really in there, after all: silicon, some plastic, some aluminum and a nice layer of bits. That's, what, $50 worth of materials?
The value isn't the bits, the value is the WORK. This is the same reason why I pay for a haircut, despite the fact that I leave with LESS than when I came in.
The only one imposing anything on anyone else is you. The author of a work that has posted it in an app store in an attempt to make revenue is playing by all the rules in their game--you're the one circumventing them and it's bullshit. You have no moral justification for your actions. If you use the application that was made, pay for it. If you don't, don't. But don't try to tell me that you get to use it and not pay for it.