Business Objects XI comes with a version of the Java Runtime Environment JRE.  When you edit a WEBI document, Business Objects verifies you have the JRE installed. If you do not have it installed you will be prompted to install it.  There may be instances where you to manually install the JRE, and here is the path for the download

This is the path for the Java JRE download.

C:\Program Files\Business Objects\Tomcat\webapps\businessobjects\enterprise115\desktoplaunch\JavaPlugin\Win32

If you have a physical three tier environment, this will be on your Tomcat or your Java Web Application server.