A Mac OS X Server developer designs, develops, and implements software applications for Apple's Mac OS X Server, an operating system designed for server configuration. They typically work with programming languages like Swift, Objective-C, and C++, and use tools such as Xcode for development. Their responsibilities involve creating server-based applications, debugging and resolving issues, enhancing server performance, and ensuring the security of the server. Moreover, they may also design user interfaces, integrate databases, and collaborate with other team members to ensure smooth server operations. They must stay updated with the latest Apple technologies and updates.