The Digitization Of Sierra Classics Initiative (TDOSCI) is a movement aimed at ActiVision Blizzard (who own Sierra and their catalog). Its creator believes that a large portion of Sierra's games aren't available digitally on GOG.com, a digital distribution platform service primarily focused on bringing DRM-free classic and indie games to consumers for affordable prices and are only obtainable for anything up to three-figure amounts via sites such as eBay, something which they believe is too expensive for non-collectors.
Roberta Williams' "Laura Bow Mysteries", Christy Marx's "Conquests", and Jane Jensen's "EcoQuest" franchises are just a few prime examples of the roughly 30 games from Sierra (and their partner Dynamix) which aren't currently available digitally via GOG.com -- The full list of games can be found on the 'Get Involved' page, and all the box art images on that page are click-through links to a GOG Community Wishlist for the specific game.
TDOSCI's creator had this to say: "TDOSCI is all about bringing Sierra Classics currently unavailable digitally to GOG.com, instead of only being available on sites such as eBay for prices unrealistic for the average consumer. Activision Blizzard has only covered their biggest franchises with a GOG Release, such as collections of Gabriel Knight, King's Quest, Leisure Suit Larry, Phantasmagoria, Police Quest, Police Quest: SWAT, Quest For Glory and Space Quest... And more recently Freddy Pharkas: Frontier Pharmacist and SWAT 4: Gold.
Sierra (along with Dynamix) released roughly fifteen games yearly throughout the 80s and 90s, and a lot of these aren't on GOG... One thing I want to make clear is that we're not trying to make sellers on eBay lose out on a sale, most of these sales actually go to collectors who have the expendable income to afford the (fairly priced) prices to bolster their collection... Simply to make these affordable in digital form to Sierra Fans."