Comment from YouTbe user NullPoEx: Copyright should expire when a product is no longer commercially viable in its original form. IE, when a game is released for MS DOS, the game's original release should become free to distribute when Microsoft drops support for MS DOS, making the game no longer commercially viable. Any re-release should be categorically different enough to justify a NEW copyright and should be measurably improved over the official release, containing either new features or significant improvements to its graphics, sound, and code to present it as a derivative work. Simply porting it to a new platform isn't sufficient.
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