A JBehave developer is responsible for implementing Behavior-Driven Development (BDD) in Java applications. They write user stories, scenarios, and acceptance criteria in a language understood by both stakeholders and developers. This helps in bridging the gap between business and technical teams. They use JBehave, an open-source framework for BDD, to run these stories against the application. The JBehave developer is also responsible for setting up and maintaining the JBehave environment, creating step definitions for scenarios, and integrating JBehave with other tools for continuous integration. Their work ensures that the software behaves as expected and meets the business requirements.