descreen fourier (fft) does not work like instructed. It there a fix?

Hi,

I am trying to get an fourier(fft)-descreen filter to work with my version of Gimp.
with no success, help needed please!

I run Gimp 2.6.11 on an iMac 64-bits with Mac OS X Version 10.7.5 (Lion)
I followed the instructions on: http://registry.gimp.org/node/19596
and placed the files in the respective directories.

Result:
"Descreen" appears in the "Filters">"Enhance" drop down menu.
"Descreen" does not appear in the "Filters">"Generic" drop down menu like the Readme.txt file stated.
When I try to descreen an image I keep getting the message: "This script requires the FFT plug-in"
Does anyone know how to fix this???

It appears that a variable named "plug-in-fft-dir" is not defined in the descreen.scm script file, for I
looked in the "descreen.scm" file first 14 lines:
1 ; Descreen v1.0
2 ; Tested on Gimp v2.6.8
3 (define (script-fu-descreen image drawable sensitivity selectiongrowth despeckle middle-ratio)
4 ; This script requires the FFT plug-in which provides FFT forward and FFT inverse filter^M
5 (if (not (defined? 'plug-in-fft-dir))
6 (begin
7 ; Display an error message
8 (gimp-message "This script requires the FFT plug-in")
9
10 ; Abort the script
11 (quit)
12 )
13 )
14
...
...