Found using GlassFish ESB v2.1 nightly build (20090508-0102).
When creating an IEP project from scratch, I observed warnings during XML Validation of CompApp containing IEP 
project. They are just warnings, so I am able to build and deploy. The warning is related to the File BC being used to 
output. 

Steps to reproduce:
(1) Create an IEP project (e.g. simple StreamInput to 3 StreamOutputs), and save
(2) Add IEP project as JBI module in a new Composite Application
(3) Build and save the CompApp
(4) Change the CompApp, for example, remove SOAP BC and add/connect File BC for inbound events
(5) Save the CompApp
(6) Either hit "XML Validation" icon or close/reopen CompApp invoking XML Validation
As a result the following warning is observed:
WARNING: The multipleRecordsPerFile attribute indicates multiple-record processing, but no record delimiter is 
defined. If the records are intended to be read from a file, define the recordDelimiter attribute, or define 
maxBytesPerRecord to process fixed-length records. If the records are intended to be written to a file, specify the 
recordDelimiter attribute or set addEOL attribute to 'true' to demarcate the records.

Workaround:
Modify IEP Module's wsdl by:
   * adding "recordDelimiter="LINE FEED"" in message section of the File binding
   or
   * changing multipleRecordsPerFile="true" to "false"
   *** Note that changing addEOL="false" to "true" does not work
Save IEP wsdl, rebuild CompApp, run XML Validation on CompApp