Java CAPS is the commercial, enterprise-class, and supported suite for building composite applications on a SOA. OpenESB is the open-source implementation of an ESB built on JBI which does not have a commercial version yet. Future versions of Java CAPS may have technology that comes from OpenESB and related projects.
Those interested in a beta release of OpenESB and the related tools should take a look at the Java EE 5 Tools Bundle Beta at http://java.sun.com/javaee/downloads/index.jsp