You are right, this format was designed for "Glest: Duelfield", and it includes mutiple textures per mesh, and other features that are not really being used in the game yet.
I probably won't have the time to update the format spec, but you can take a look to the Model::load() method in model.cpp in the game "shared library 0.3-rc1" (that as the name indicates is the function to load a model from disc).