A GData developer is primarily responsible for creating and managing applications that interact with Google services. They use Google's GData protocol, an open standard for data exchange, to access, update, and manipulate data from Google services like YouTube, Google Calendar, or Google Docs. Key tasks include developing code, debugging, testing, and integrating Google services into existing systems. They also ensure data security and privacy, and troubleshoot any issues that arise. Their role requires a deep understanding of APIs, XML, and HTTP protocol, and strong programming skills, typically in languages like Java, Python, or PHP.