I finally stopped tinkering and delaying, the source to Giselle is now available from the Aqsis SourceForge git storage. It's in its own repository, as I believe this tool could become quite big over time, so didn't want to overload the Aqsis repository.
You can get the source from git using...
git clone git://aqsis.git.sourceforge.net/gitroot/aqsis/giselle
Building shouldn't be too difficult once you have QtCreator installed. You'll need to make sure that swig can be found, this can be done in the Build Settings tab in QtCreator's Projects section. Also in there you'll need to set AQSISHOME to the installation location of Aqsis and it's libraries/headers if they are not in a default place your compiler can find them.
To run once you've built it, you'll need to edit the Run Settings environment to include the lua/luagl/luari output folders in the PATH or LD_LIBRARY_PATH for Linux.
All this should become easier once I setup a proper install target that packages everything in the right place. I'll be setting up a section in the Aqsis Wiki for Giselle soon, so all this will be described there in more detail. Any problems, pop into IRC or mail me.
The main reason for releasing this at this point in it's development is to get feedback, so please take a look and make any suggestions (or indeed offers of help ;) ).