> To be sure, using the term "risk" in the context of licensing speaks quite clearly in my mind of interests aligned with commercialization (or the prohibition thereof).

In principle at least, unclear licensing is a legal risk even to non-commercial users. If someone posts stuff on GitHub without any clear license, and I then fork it and makes some modifications as part of some non-commercial hobby project, and then the author of the original project sends a DMCA takedown notice against my non-commercial hobby fork, then legally I would not be in a very strong position. (Of course, in practice, this is unlikely to happen very often, but I suspect something like this probably does on rare occasion.)