Perhaps it was, but it is very difficult to create a strong copyleft licence that is not the GPL that is compatible with the GPL, and that goes for any strong c

Perhaps it was, but it is very difficult to create a strong copyleft licence that is not the GPL that is compatible with the GPL, and that goes for any strong copyleft licence in every direction, so much so that GPLv2 is not compatible with GPLv3. It's rare to find two strong copyleft licences that are compatible with each other — advocates of strong copyleft typically phrase their arguments as if there only be one strong copyleft licence in existence, as this is the major problem that is hard for them to overcome that is seldom sung.