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2: Atari never supposed that anyone else would develop games for their system and took no measures to prevent it. When Nintendo developed their Famicom system (called the NES in the United States) in the early 1980s, they included both legal and hardware measures to prevent unauthorized development for Nintendo consoles. This has become the industry default in the years since.
3: Atari earned very little on the sales of individual console systems. The bulk of their revenue came from the sales of games. When Activision opened the floodgates to third-party developers, that revenue started to dwindle. The crash of the 2600 was caused by several factors (ageing technology, growth in the home computer market, rival console systems), but the flash-point seems to have been a wave of new developers, and their subsequent collapses (which forced retailers to liquidate that inventory [and Atari to drop prices to match new market expectations]). (Tristan Donovan, Replay: The History of Video Games, pp 98-99)
4: Wizards of the Coast purchased TSR (the original publishers of Dungeons and Dragons) in the late 1990s, rescuing the game from financial collapse. When they decided to publish a 3rd edition of the game, they also created the Open Gaming License. It allows for groups to publish works derivative of the system that powers Dungeons and Dragons 3rd (and 3.5) edition. They also created a subset of the OGL called the D20 license. The D20 license was more restrictive, fluctuating (and needed the approval of Wizards of the Coast) but had greater name cachet. (R. Dancey, “Open Gaming Interview with Ryan Dancey,” http://www.wizards.com/dnd/article.asp?x=dnd/md/md20020228e )
5: The motivation behind the OGL was two-fold: one it was designed to promote sales of Dungeons and Dragons products (M. Cook, “The Open Game License as I See It, Part I”, http://www.montecook.com/cgi-bin/page.cgi?mc_los_154 ); and two: it was designed to prevent Dungeons and Dragons from ever disappearing down a rabbit hole of legal entanglements in the event that Wizards of the Coast (or some future copyright holder) should go out of business. (R. Dancey, http://paizo.com/paizo/messageboards/community/gaming/4thEdition/mikeMearlsHasOpenGamingBeenASuccess&page=4#156 )
6: There are no clear numbers for the titles and quantities sold of OGL and D20 products. There were a lot of them. (Just searching for D20 on Amazon gives you 176,000 hits. Even accounting for duplicate results, that’s a lot of them! And of the OGL/D20 split, D20 was the far more restrictive!)
Interestingly, Dungeons and Dragons’ current biggest rival in the role-playing game market is the title Pathfinder (created by former Wizards of the Coast partner Paizo), which uses the OGL to carry on the now discarded 3.5 edition of Dungeons and Dragons.
When Wizards of the Coast released their 4th edition of Dungeons and Dragons in 2008, they created a new license, called the Game System License. It is much more restrictive than either the OGL or the D20 licenses. I do not know the rationale behind the changes, though certainly, on the surface, it looks to be intentionally more protectionist.
7: Retailers purchase role-playing games from distributors up front; in doing so they place their financial well being on the line with every product they stock. They must gauge quality against local demand with every game they purchase. While they invariably purchase games of lesser quality when an audience (or trend) demands it, on the whole, they must act as industry arbiters.