Loading python scripts to OSX Mac computer on Leopard.
I run and installed Gimp under X11 .
I finally got my Plug-ins to work for me!

If yours is like mine.. X11 and you installed by dragging the application from a
downloaded .dmg this might do the trick.
*Setting the folders in Edit/Preferences/folders didn't work for me.
Here is what I did.
FIRST STEP ... Note: "xxx" is the name of YOUR script
For convenience, store "xxx.py" plug-in script "XXX.py" on the
desktop.
Now here is the tricky part.

Open "Applications" and
RIGHT click Gimp.
There should be "Show Package Contents" in the pop up menu.
RIGHT click it.
You should see "Contents"
Now lets navigate to where the script needs to go.
RIGHT click Open "Contents"
There should be files and folders one of which is "Resources".
RIGHT click Open "Resources"
There should be a folder "lib"
RIGHT click Open "lib"
Find the folder "gimp"
RIGHT click Open "gimp"
There should be a folder "2.0"
RIGHT click Open "2.0"
Find and RIGHT click OPEN "plug-ins"
Here I found a lot of black Icons with names.
I scrolled all the way down to the bottom and found files with a ".py" extension
I dragged my Python script from my desktop into this window of files.
Basically I navigated to:
/Applications/Gimp.app/Contents/Resources/lib/gimp/2.0/plug-ins
and dragged my script file from my desktop (Meaningful Black.py) to the open folder window
and dropped it in.
Note :to navigate in the terminal ..( But, I don't know why you would need to do that. )
Open the terminal and first type
cd //
then, cd applications/gimp.app/contents/resources/lib/gimp/2.0/plug-ins
Then I restarted Gimp and there is was. Just where it was programmed to be!
My Python script was "Meaningful Black.py" and
it located itself in /Filters/Enhance.
I didn't do a terminal command:
chmod u+w xxx.py
from the terminal to that navigated location.
Apparently these permissions are assumed.
EDIT: I loaded another *.py script and the execute permissions were not set so I
did have to set them. Thus, navigate with terminal and chmod u+x
filename.py.
Hope this helps.. let me know and respond.

Dan