A Gnuplot developer is responsible for creating and managing data visualization using the Gnuplot software, a portable command-line driven graphing utility. They translate complex data into readable graphs and charts to aid in data analysis and interpretation. Tasks include writing scripts, debugging, modifying existing codes, and optimizing performance. They work closely with data analysts and scientists to understand the data requirements and produce effective visualizations. They also ensure the accuracy and reliability of the plots and may be involved in improving the software's functionalities and features.