>>12
It's easy to understand the logic here. Some of the people that claim the GPL is non-free want the power to fork free software and make the fork proprietary software; the logic being that one is more free if one has the power to make proprietary software from free software. The other logic used is: more rules means less freedom; since the GPL has more rules, it inherently has less freedom.
The logic that the FSF folk use is that: all users should have the right to use, study and share all software within their possession. The reason for this is so that each individual can maintain complete control of their computing (the freedom to help oneself) and be able to be good citizens (as good citizens share resources). Any software that doesn't adequately meet their definition of free software is proprietary software.
The FSF folk claim that the ability to fork free software into proprietary software is harmful to socitey and so, created the GPL with the intent that nobody can make a proprietary fork of a GPL program and thus, users will remain free.