What license covers the documentation? I found no mention of any
copyright or license notice in the documentation. GPL? GFDL? By default
it is a proprietary license, according to copyright law.

2/ Is the documentation retrieved with the following command:
-=-=-=
wget -km -np -A pdf http://prdownloads.sourceforge.net/greenstone/
-=-=-=

the latest versions of all documents? Are new versions or updates
planned soon? Are there HTML versions of the documentation?

3/ The documentation was written in what format (DocBook?) Are the
sources and compilation suite used to produce the PDF available?