The Openfire plugin developer guide states that 'additinal' files should be in /classes/. Apparently, the old Ant script also included any files in the /src/. The new Maven structure does not.
To work around compatibility issues, code that was in /src/ is now moved to /classes/. This should work with both Ant, as well as Maven.

Additionally, this plugin now makes use of the new HttpBindManager API for registering contexts with the BOSH context. I do wonder if this plugin has any reason to be here though. Can't it just run its own embedded Jetty server?