Holodeck B2B is an open source implementation of ebMS3/AS4. It's fast, lightweight, easy to install and very flexible. 

In the latest release of the popular open source AS4 MSH the modular architecture of Holodeck B2B is taken a step further - making it even more flexible. 
A P-Mode validation function is added, to separate validation from internal & external storage. Using the API of this module you can choose your own method of adding and storing P-Modes. It also lets you apply domain specific guidelines to P-Modes.

Storage of message units has been separated from the core, with an API that allows you to choose your own persistency solution. 
Also new are unit tests and integration tests to further improve code quality.

Of course a default implementation for P-Mode validation and persistency is included in the download, meaning that Holodeck B2B still works out of the box. 
Download it today on holodeck-b2b.org