> ...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.
In agreement with the pragmatic implications, but I still genuinely struggle to see the point. The financial constraints of legal defense is what strikes me as the killer of non-commercial hobby projects if the hypothetical scenario would arise; with or without appropriate licensing terms, there's really nothing to stop an original project with the financial means and intent from issuing a DMCA takedown and outspending an unfunded project in legal maneuvering. IANAL but at least it sure does feel that way in my limited experience.