The EJB Connector for Mule 4 establishes communication between Mule applications and EJB, integrating EJB business logic across WebLogic and JBoss servers. It retrieves data from EJB systems, supports custom service packages, and is compatible with Mulesoft v4 and Java 1.8 or later. Use cases include ERP integration for real-time customer data synchronization and data aggregation for generating reports across multiple systems.