Limited documentation is available in the app ZIP file in the "doc" folder that you can download.
Details for configuring the application for deployment can be found in the configurationDefinitions.html file.
The Readme.txt contains some commands to run the app.
This is an excellent detailed document covering setting up and using the OpenAS2 application: http://www.ibm.com/developerworks/websphere/library/techarticles/1101_barrus/1101_barrus.html