A Gosu developer specializes in using the Gosu programming language, primarily for the design, development, and maintenance of Guidewire applications. This includes creating business rules, integrating with other systems, and troubleshooting issues. They also conduct code reviews, optimize performance, and ensure software quality through testing. The developer collaborates with other IT professionals to understand requirements, develop solutions, and provide technical support. They need a solid understanding of Java, XML, and web services, and must stay updated with new Gosu developments and best practices. Their work is crucial in developing robust insurance applications.