You can try our Discorso Framework (http://www.velare.com/product/overview.htm
It implements a multiple binary collaboration model but has natural ability to implement the Webservices Orchestration as well.
Discorso has some advantages in comparison with BPEL4WS and Collaxa: you can develop everything using pure Java without any proprietary extensions, tags, and preprocessing. And you can use all OOP techniques, patterns, any existing Java IDE and/or modeling tools for your development.
BTW IMHO orchestration approach is not very suitable for real B2B applications, where all partners should be able to have their own business process implementations. In case of orchestration you actually have master-slave relationships between Master Orchestration Server and Webservice-slave.