Hi Steve
Welcome to the sgs group.
Unfortunately I need to say that Thomas had left without notice. Last message was in 2013. There is currently no dev team.
For the moment we are just maintaining the current version 0.745 to keep sgs running and useful. For this I created a fork on github to secure any useful information:
There, I maintain a patched version
0.745p with a conservative patching policy. I include patches if they pass test by a third person to secure the quality of the code.
I help also with patching and solving problems if it is feasable for me. This also holds for every active member of the forum. New ideas are best contributed by the extension mechanism.
This forum here is the only place I know still to be active. Obviously there is a need for further development and also ongoing maintenance to keep sgs in pace with php and some contributed libraries. But for the moment, the users will tell, when they run into a problem and we simply try to solve it.
You will find the whole documentation in the documentation folder under the link above in form of pdf files.
There is also a archive of the official website but you can still use the official website. There is an error somewhere in the links, but starting from this link here you should be able to reach any part of the documentation as far as I tested, including how to develop custom modules:
Don't hesitate to share your contributions and we check if we can push forward on a case by case basis. A new dev team would obviously be a great benefit as sgsml allows also to non-developers to create their own customization fearly easy.
Cheers
Patrick