Sorry for the delay, everyone but I was tied up with other things ...
I just managed to wrap up a beta version of the GRASS Extensions
Manager, as announced in the latest GRASS Newsletter.
I am also providing a small sample extension consisting of an
overhauled cumulative viewshed analysis module and another one to
calculate a prominence index. Please excuse the poor state of the
documentation. I am working on it, but field season will start
soon, so don't expect too much before autumn.
You can download the files from my (German) homepage:
This should download and install the extension including HTML docs and
GIS Manager entries. If you restart GIS Manager, you should find a new
'Xtns' menu. HTML docs are accessible from the main GRASS index.html.
Please look for more info in the README file and let me know how it
works for you. I would be thankful if someone could compile and try
this program on MacOS X and CygWin as I do not have access to such a
system right now.