Licensing
The SDK itself is a free download, but beta SDKs require a paid developer account. In order to release software, one must enroll in the iPhone Developer Program—a step requiring payment and Apple's approval. As of September 2012, cost of enrollment in the iPhone Developer Program is US$99 per year (the cost varies from country to country) for the standard program. Signed keys are provided to upload the application to Apple's App Store. Applications can be distributed in three ways: through the App Store, through enterprise deployment to a company's employees only, and on an "Ad-hoc" basis to up to 100 iPhones. Once distributed through the App Store, a developer can request up to 50 promotional codes that can be used to freely distribute a commercial application he or she has developed. The SDK can only be installed in Mac OS X, and the latest SDK (iOS SDK 6.0 with Xcode 4.5.1, as of October 2012) requires OS X 10.7.4 "Lion" or later.
Read more about this topic: IOS SDK