Just re-read my comment and want to make sure I don't get misunderstood: the comment does not apply to the entire PR!

If I'm right, just the anfft/FFTW import(s) need to be removed. AFAIK you could hardcode `ANFFTMOD = False` and leave the rest, because then it wouldn't be "linked" which is the GPL v3 danger word. Then users, individually, could replace that hardcoding with the original `try/except` statement if they so wished, for their own purposes. We just can't have *link* there in official scikit-image distributions.

It might even be OK to leave the `try/except` block there, just commented out with an explanation, but I'm not certain of this.