The Story of My Life has a character obsessed with It's a Wonderful Life, and they share a few similar themes, but the musical is not an adaptation of any source material, which is what I consider the main criterion of an "original" musical to be.
The title of Passing Strange comes from Othello, but the musical itself has nothing to do with it, ha. (Do you think it does?)
Even Chaplin, Scandalous and The Scottsboro Boys I would consider original musicals, despite their bio-nature, unless they were specifically adapted from one (auto)biographical source.
If we are talking about the repackaging of a cultural product for the Broadway stage then The Story of My Life and Passing Strange are certainly not that.
For the record, I don't think a musical being "original" makes it any better or purer than a musical adapted from source material.
Marie: Don't be in such a hurry about that pretty little chippy in Frisco.
Tony: Eh, she's a no chip!