Twister is a WS-BPEL compliant Business Process Engine, providing web services invocation and direct end-user interaction using a worklist. It lets you deploy your processes described in WS-BPEL in the engine that will execute them. It will acknowledge the messages you send and produce new messages invoking any service or creating work for a human particpant.

New features in this release include:
    * Web Services invocation based on provided WSDL.
    * Process versioning (re-deployment, suppression, ...).
    * Enhanced user management.
    * Synchronous invocation involving several activities (receive and reply don't need to follow each other anymore).
    * Cleaned up configuration.
    * Bug fixes.

http://www.smartcomps.org/twister/