Support has confirmed that there is no easy way to clone a third-party module for use in your active child theme. There are many reasons why this would be helpful, with the primary justifications listed below:
1) Ensure approved modules for staff are all in the same place (under your “theme” tab).
2) Ensure the module style choices are exclusive to your brand so your staff isn’t tempted to do something inconsistent with your theme.
3) Remove, add, or edit the cms/html/js natively so there wouldn’t be multiple style sheets called for that would slow down your site.
If the module is indeed “free”, it should be easier to clone and customize it while at the same time leaving attribution in the code.