<sarcasm>Really? SDK is used for software development. You don't say.</sarcasm>
So, a regular iPhone owner is going to use the SDK to get an application running on it? Please!
The point is that Apple are worse than Microsoft. They'll use any monopolistic practice in the book to exclude others from interoperating without paying rent (in this case the ugly DMCA - possibly the ugliest of all private monopolies). And all that while using open source software for the basis of all this. Pathetic.