Forum OpenACS Q&A: Re: What about Workflow package?
I would definitely recommend acs-workflow. It's a great package which we've used extensively in Quest. I also know that Project Open use the Postgres version a lot too. http://www.project-open.org/en/package_acs_workflow
See this thread for some background http://www.openacs.org/forums/message-view?message_id=329333
feel free to ask any questions!