Earlier quoted context omitted.
You have the right to use this project via git submodules. The GitHub terms of service requires code owners to allow forking and linking to their public repositories, regardless of license.
It does not appear to grant (or attempt to grant) use of the software. So sharing and forking are fine, but not necessarily anything else. > 5. License Grant to Other Users > Any User-Generated Content you post publicly, including issues, comments, and contributions to other Users' repositories, may be viewed by others. By setting your repositories to be viewed publicly, you agree to allow others to view and "fork" y…
Did I imply otherwise? Git submodules are just links. Please explain how linking to a submodule is not allowed.