Well, I believe in sharing everything.
I share files, I share code, I share what I eat and drink, etc.
From my point of view, it's hypocritical of someone who makes free software, to make the logo which represents that software, not free.
As far as the two things being different, well, I think that since the logo DOES represent the free software, it should be free as well, because it is part of it.
The very fact it represents the free software makes it a part of it.