in simple terms, what is the process for converting a movie shot in 3D to 2D format for DVD release?
Assuming the movie was actually shot in 3D (and not fake post-production 3D which looks like shit) then the process is pretty straightforward: for each shot, simply choose one of the two stereoscopic images, whichever looks better.
Basically, the editor has the computer close one eye while copying to the disk.