Take a look at FolderPermissions.vbs at:
http://213.105.197.62/scode/Code.htm

This should return the groups or users for the roles  for each folder.
You might need to use ADSI to determine who is in a group.

I tried to use the info you gave me, but it's to technical for me,
and our gourou wasn't available until now .
But, if someone should be interested : I found this neat dwp :
http://www.greenfel.demon.co.uk/scode/WebParts.htm
in the <www.greenfel.demon.co.uk/.../MiscWebParts.zip>
MiscWebParts.zip where you can find a webpart that shows authors  and
coordinators for all folders in the document Library.

There's just one hic : your folders should'nt have names with accents ¨é or
è etc, because then the script doesn't work.

There's two web parts/scripts out there that can be combined to provide
this. The listfolders.vbs from sharepointcode.com will iterate through
and dump your entire folder  structure. There's another web part (I think
from the same site, can't remember) that will display security  settings
for a given folder. Take the code from this and combine it with the
listfolders script and you'll have a dump of all the authors. You might
want to format the output to be a csv file or something then import it
into a spreadsheet or database and remove duplicates.