Right, you had a question. If you're concerned about infringement, you should register both the first version and the most recent version, and you should probably do the same for all platforms. Yes, it's true that you get copyright automatically once you create a work. But in reality, the copyright is not so automatic when you want to sue someone. That's because you have to file a registration before filing your suit. When completing the application, the Copyright Office rules require that you (1) list the first date of publication, (2) that you acknowledge any preexisting material that you incorporate in your version, and (3) that you deposit the best edition of the first publication. Those three criteria can cause confusion. That's because software programs (like video games and websites) go through a series of substantial changes after they're first offered to the public.
Date of first publication; preexisting material. The Copyright Office wants you to provide the date of first publication for your software program. But if you're offering a series of version, each constitutes a separate "first" publication. For example, there's a first publication for your iPod version, your iPad version, your iPod 2.0 version, your Android 3.0 version, etc. And whenever you register your work you can claim only what is new over the previous version. As a result, you must file a series of registrations as described here.
Depositing the best edition. Consider the software developer who no longer had the first published version of his source code from 1990. In order to deposit the first published version, he reconstructed it by removing all of the code he'd added since the program was first created. Not good enough said a court who claimed that reconstructions of code would not suffice. Therefore, we hope you have maintained copies of the source code for each version and you can furnish it according to these requirements. P.S. For more exciting legal info on apps, check out our O'Reilly Mini eGuide.