Does this rental hocus pocus hold up in an American courtroom? If not, why not?
I don’t know, but I believe software is licensed, not purchased, so I don’t see why it can’t work for music (but I’m not a legal expert).
And does dina d’malchusa apply?
I wonder the same thing (I’m not a halacha expert). If so, then it should also be okay to use someone else’s tune (the royalties are pennies per copy sold which is usually insignificant in the Jewish music market; they would be chayav, but the amount would be small).