Seasons of Stargate SG-1 have been released on DVD in a variety of countries. The content on the various disks, including "DVD extras" varies widely depending upon the space on the respective disk and language and marketing considerations for various countries. Region 3 DVDs may have different contents than Region 1 DVDs. Region 2 Belgium DVDs may have different content than Region 2 British DVDs. The release dates of the different seasons varies by country, though most sell the DVDs in box sets by season.
A lot of production information, including production notes, concept drawings, behind the scenes stories, and interviews with cast and crew are provided in the various DVDs of the program. These articles list the contents of the various DVD releases of Stargate SG-1.
NOTE: DVDs manufactured for different geographic regions are not interchangeable. Most Region 2 DVD players will not play a Region 1 DVD and vice versa. Sony/MGM have released the various seasons with different extras on the DVDs. You can find more information about DVD regions here: http://hometheaterinfo.com/dvd3.htm