Regarding my version 4.3.0 with the "galleryconfig" error. You are the second person to have this, so it must be some weird issue (works on all my sites). Make sure the dotnetnuke.modules.gallery.dll file is in the bin directory and try moving it out of the directory and back in and see what happens to your error messages as you do that..
As for documentation, I have a short FAQ about the gallery. For the most part it (should be) so simple that you don't need documentation.
The official status is that the Gallery 3.0.12 is a beta module (last released over 2 years ago). There is a team of people who were working on getting a release out sometime around Dec 2006 (yes 2006).
Currently, the lead of the project is Chris Paterra. He has been very busy (he also works on the forum module) and hasn't had much time to do further work on the module. Adeian is Paul Davis, yes he is listed in the team members. Hooligans is Nester Sanchez. yes I wish we didn't use aliases for names. I have seen my name on the list of Gallery team members for the past 10 months, but as of yet, I still don't have any access to modify the code, change the website, look at the private forums, modify gemini, etc. So I'm not even sure why my name is up there.
As for the Gemini issues, I have fixed all of the major issues in my version of the code.
As always, my code is on my website: www.Jegers.com