A JRun Developer is a software engineer who specializes in using JRun, an application server from Adobe Systems for Java applications. They develop, deploy, and manage applications to meet business needs. Their responsibilities include writing efficient code, debugging issues, and ensuring optimal application performance. They work on application integration with databases and other systems, and may also be tasked with securing applications against threats. Additionally, they often work in cross-functional teams, collaborating with other developers, systems analysts, and project managers. Furthermore, they are expected to stay updated with the latest industry trends and advancements in Java and JRun technologies.