If you’re working with the Mule IDE, the Mule source code is automatically attached to the Mule JARs. This allows you to browse and step into the source code while you’re developing Mule applications. The Mule IDE looks for files with the naming convention mule-*-src.zip in $MULE_HOME/src and automatically attaches them to the Mule JARs.
If you’re evaluating Mule Enterprise, the source code is not included with the Mule download. To attach the source, simply download the Mule community source code ZIP file into the src directory under your Mule home directory and restart Eclipse.
If you are already a Mule Enterprise customer, you can download the community or enterprise source code ZIP file from the Downloads page on the customer portal. The enterprise souce code has additional classes not available in the community source and is available to Mule Enterprise customers only.