Because it seems like it might have been lost in the (unavoidable, understandable) lag time and overlapping threads:
The vast majority of the software on MELPA that we're talking about *is* free (open, libre, beer-and-speech, etc.) software - most of it GPL. This is why so many people who care about both emacs and free software decide, in the end, to use and/or recommend MELPA to users. For example: Tuareg was mentioned earlier. It's GPL software for editing OCaml in Emacs. This is why at least some people don't think that it's poisonous, thorny, or otherwise "bad fruit". Unfortunately, it's "good fruit" hanging from a tree that grows in an orchard that also has some trees with bad fruit, to push the analogy too far.
I hope that helps,
~Chad