A Lean Software Development developer focuses on optimizing efficiency and minimizing waste in the process of software creation. They prioritize delivering value to the customer through iterative development. Their responsibilities include understanding and implementing the seven principles of lean software development: Eliminate waste, Amplify learning, Decide as late as possible, Deliver as fast as possible, Empower the team, Build integrity in, and See the whole. They use tools such as Kanban and continuous integration to streamline processes. Their role involves constant collaboration and communication with stakeholders to ensure alignment with customer needs and project objectives.