Do writers working for us who have thier own RISE 360 License need to also have seats on our Rise Account?

I have 2 Rise authors working for me. They both have thier own Rise accounts. They both need to be able to access Rise courses we have in our Rise account.

Do I need to make them team members (buy seats for them) in order for them to access and modify our existing Rise content, or can I just share the content with them, and let them update it and then have them share it with me once they have created the new work?

Of course we want to "own" (manage and control) whatever RISE 360 publications they produce for us, whether it's a revision or a new work. So will "sharing" Rise files (between licensed Rise users) support this, or do we need to buy seats for them and work with them as collaborators and managers of our shared files, and have them upload their finished work product to our RISE account? This is really a question about whether or not it is necessary to buy seats for employees / contractors who already have their own RISE license.