They are not actually incorrect. The FSF it as non-free too.
The direct quote from https://www.gnu.org/software/for-windows.en.html#f2 is
"Why not recommend Firefox? As explained in our Free Software Definition, all
four freedoms must be available on both a commercial and non-commercial
basis. Mozilla's trademark policy serves to limit Freedom 2 to gratis
distribution only, making the software nonfree."
What Mozilla is doing via trademark law to remove part of the 4 freedoms is
not common so I don't necessarily expect you to pick up on all of the
subtleties so I'll try to go over everything.
Where does that non-commercial requirement come from? I blogged about it a
few years ago:
https://jxself.org/mozilla_trademark.shtml The quote from their trademark
policy is:
"If you want to distribute the unchanged official binaries using the Mozilla
Marks, you may do so, without receiving any further permission from Mozilla,
as long as you comply with this Trademark Policy and you distribute them
without charge."
You can even go to https://www.gnu.org/philosophy/free-sw.html and see where
it says that "'Free software' does not mean 'noncommercial'. A free program
must be available for commercial use, commercial development, and commercial
distribution."
That includes charging.
Brett Smith from the FSF also confirmed it:
http://lists.nongnu.org/archive/html/gnu-linux-libre/2011-08/msg00014.html
The Trisquel Project invoked Freedom #3 and turned it into Abrowser, so as to
restore the missing part of Freedom #2 (the ability to distribute exact
copies commercially.) But the software as you get it from Mozilla doesn't
directly come with Freedom #2 intact. And when all four freedoms are not
available, or are insufficient, it's non-free software. In following our
community guidelines we don't provide help for non-free software.
https://trisquel.info/en/wiki/trisquel-community-guidelines
