It's not misquote, it's paraphrase.
[1] http://dictionary.reference.com/browse/paraphrase
[2] "It has been said that democracy is the worst form of government except all the others that have been tried.”" -- Winston Churchill
PS: Don't rely too much on dictionary.com, it's not the best. E.g. the New Oxford American Dictionary correctly gives the second meaning of "paraphrase: a rewording of something written or spoken by someone else".