Flowable Work and Flowable Engage are licensed and not free. They have the open source engines at their core, but different UIs for designing, running and administering Flowable. They also have many additional services for building complete enterprise solutions. There’s lots of public documentation available here that you can explore to see the additions.
There’s a 30 day trial download of the enterprise product available from here. On the flowable.com site there are contact request forms that will allow you to be contacted by the relevant salesperson who can give you guidance on pricing.
There’s a separate enterprise forum we encourage people to use if they have specific questions on the enterprise product, to minimize noise in the community forum.