According to Getting Started guide the Xalan JAR is only required for HTML and PDF export. I am not using either, however I get a runtime exception when calling XmlUtils.deepCopy():
Exception in thread "Thread-5" javax.xml.transform.TransformerFactoryConfigurationError: Provider org.apache.xalan.processor.TransformerFactoryImpl not found
If I add xalan-patched-2.7.0.jar, deepCopy starts working without throwing any exceptions.
Getting Started says that Commons-VFS is needed for "Saving/loading via WebDAV etc". But it appears that it is used by WordprocessingMLPackage.load(). If I remove the jar, the following exception is thrown:
Exception in thread "Thread-5" java.lang.NoClassDefFoundError: org/apache/commons/vfs/FileSystemException
It's not a big problem as such, but perhaps the documentation should be updated. Ideally, of course, I'd have as few external dependencies as possible.