(?:`)?(?:bison`exception)?(?:`)?as`a`special`exception,`you`may`create`a`larger`work`that`contains`part`or`all`of`the`bison`parser`skeleton`and`distribute`that`work`under`terms`of`your`choice,`so`long`as`that`work`isn`t`itself`a`parser`generator`using`the`skeleton`or`a`modified`version`thereof`as`a`parser`skeleton\.`alternatively,`if`you`modify`or`redistribute`the`parser`skeleton`itself,`you`may`\(at`your`option\)`remove`this`special`exception,`which`will`cause`the`skeleton`and`the`resulting`bison`output`files`to`be`licensed`under`the`gnu`general`public`license`without`this`special`exception\.`this`special`exception`was`added`by`the`free`software`foundation`in`version`2\.2`of`bison\.