It would appear this is no longer true--GOG seems to have decided on the CD version for both the Galaxy and Manual install routes..."GOG 14". I wouldn't have noticed except that I formerly had the DVD version installed through Galaxy, and a savegame under the DVD version, and when Galaxy finished updating yesterday the game would no longer load the save, telling me "The CD version of Riven will not accept saved games from the DVD version"--or words to that effect...;) (The DVD version would say the same, only in reverse, if you tried to load a saved game from the CD version.) Fully deleting and reinstalling/verifying through Galaxy now results in the same installation as the Manual install, "GOG 14."

However, never could see a nickel's worth of difference between the two, and I have no idea why they dropped the DVD version of the game--if indeed this is a permanent change. However, I did notice notice that the Riven file number for the CD version was higher than the Riven.exe DVD, awhile back. I included the version numbers in another post here somewhere...

EDIT: Lol...I checked it again today and reinstalled through Galaxy again--and now the game will not accept my save from the Galaxy install yesterday of the CD version....! Apparently, things are now back to Manual = CD version; Galaxy install = DVD...version...as you pointed out above!