Just try Googling for "weak copyright" or "strong copyright". You can see for yourself that there's no such usage like you're explaining. All the top results ar

Just try Googling for "weak copyright" or "strong copyright". You can see for yourself that there's no such usage like you're explaining. All the top results are about whether copyright as a general concept is, or should be, strong or weak, applied to all circumstances (proprietary and open sourced software alike and even other types of copyrightable works). Strong and weak copyleft is a different matter, those terms do make sense. Maybe that's the source of confusion here.