None of these extra programs are required for the core greenstone
functionality, but some plugins require these external programs for
some things (these programs are all GPL or GPL-compatible licenced and
except for imagemagick are all distributed with greenstone):

* WordPlug uses wvWare to process MS Word documents (and will fall back for
.doc files that are really RTF documents)
* RTFPlug uses rtftohtml
* ExcelPlug and PPTPlug use xlhtml and ppthtml (for PowerPoint) respectively
(both part of the same xlhtml source package)
* ImagePlug uses imagemagick programs for processing the images
* PDFPlug uses pdftohtml
* PSPlug tries to use ghostscript, and will fall back to simple text extraction
if ghostscript isn't found, or fails.

In addition to those programs that are used for importing documents,
there are some other programs used, although most users won't need
this functionality:

* wget is used for mirroring web pages for import (distributed with greenstone)
* gimp/gimp-perl is used for creating new image buttons, mostly used during
translation of the greenstone interface into other languages. This is
being dropped in favour of using imagemagick for creating the buttons.

That's all I can think of for now. This is documented in more detail in
the Greenstone Developers Guide, I think.

John McPherson.