Some packages in Debian link to specific parts of the documentation that
recommended nonfree software. FSF does not like this one bit.
It is not the problem with the ISO. The ISO is just a means of distributing
an operating system for testing and installing. And then you install Debian
8, which the FSF cannot endorse. Basically, your "libre ISO" promotes a
non-free distribution in the eyes of the FSF. It is as simple as that.
Point is, anything that is Debian gets rejected. Only something like
gNewSense which is a significant amount of work purging offending packages
and anything they depend on, while being independent from Debian project is
going to get approval.
And if that is what you want, go and help gNewSense for crying out loud!
