It's quite true that the tune of Bob Dylan's Dream is based on the tune of Lord Franklin. And so what if it is? The main thing that is striking about the song Bob Dylan's Dream is the lyrics which are superb and insightful, and they bear little if any resemblance to the lyrics in Lord Franklin.

Why shouldn't someone use the tune of some old trad song, alter it a bit, and write new lyrics to it? Hell, people have been doing that for the last few thousand years. Example: The music of "The Star Spangled Banner", America's national anthem, is a recycycled tune from a popular English drinking song of the 1700s. Francis Scott Keys simply wrote new words to an old tune. ;-) Nobody seems to have a problem with that.