A GitHub developer manages code repositories using GitHub, a platform for version control and collaboration. They commit changes, create branches for new features, and merge them once completed. Developers also collaborate with other team members, reviewing code through pull requests to maintain code quality. They utilize GitHub's issue tracking for bugs or enhancements, and manage project documentation. They may also release and version software directly from GitHub. Additionally, they can contribute to open-source projects, making pull requests to suggest changes. A GitHub developer uses these tools to effectively manage and track progress, ensuring seamless and efficient software development.