Sun Java Plug-in - Version 1.3 Sun's release of Java Plug-in (formerly known as Project Java Activator) software enables enterprise customers to direct Java applets or JavaBeans components on their intranet web pages to run using Sun's Java Runtime Environment (JRE), instead of the browser's default Java runtime. This enables an enterprise to deploy Java applets that take full advantage of the latest capabilites and features of the Java platform and be assured that they will run reliably and consistently.