Both opennlp.common and opennlp.hylo have been discontinued as packages in their own right. The final releases have been made only to allow the source code of their final state to be available in conjunction with release 0.7.0 of Grok. However, many things are living on in the OpenCCG project (http://openccg.sf.net), so go there for the latest.
At the moment, OpenNLP is thus only providing the organizational role for a number of different projects. See the website for details.