for those interested

Properties properties = new Properties();

PackageBuilderConfiguration cfg = new PackageBuilderConfiguration(properties);

KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(cfg);

kbuilder.add(ResourceFactory.newFileResource("PATH_OF_YOUR_PKG"), ResourceType.PKG);

Collection<KnowledgePackage> pkgs = kbuilder.getKnowledgePackages();

for(KnowledgePackage pkg : pkgs){

     for(org.drools.definition.process.Process proc:pkg.getProcesses()){

                    InputStream in = ((org.jbpm.process.core.Process) proc).getResource().getInputStream());

                    // Now you can serialize to a Dom element for example

          }

}