That would be because:
- The copied app (unlike on the free internet) couldn't be called "Colloquy" (or reference Colloquy in its tags) because Apple would forbid its distribution, and so discoverability is significantly reduced.
- It costs $99 to acquire an appstore developer certificate to work with Apple's DRM, reducing the chances of opportunistic behavior on behalf of users. I can't just check out your project and put it online.
Of course, the app has been cracked and placed on other sites (and its technically legal since binary modifications/redistributions are allowed). But thats a different issue.
Is it really a different issue? It seems like the only thing protecting you from unrestricted copying is Apple's DRM and control over the AppStore.