River is an open source and always free workflow framework for Django which support on the fly changes instead of hardcoding states, transitions and authorization rules.
The main goal of developing this framework is to be able to edit any workflow item on the fly. This means that all the elements in a workflow like states, transitions or authorizations rules are editable at any time so that no changes requires a re-deploying of your application anymore.
This is a fully open source project and it can be better with your donations.