The Mac Developer Program is a way developers for Apple's Mac OS X operating system can distribute their apps through the Mac App Store. It costs USD $99/year. Unlike iOS, you are not required to sign up for the program in order to distribute or test your applications. Mac applications can freely be distributed via the developer's website and/or any other method of distribution excluding the Mac App Store. Apple provides Xcode for free to developers to code, build, and test their apps. The Mac Developer Program provides you with many resources to help you distribute your Mac applications.
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Mac Developer Program Wikipedia(Text) CC BY-SA