Black to the Future is a Season 22 story that never made it to the screen, instead ending up as a film starring Christopher Lloyd as the Doctor and Michael J. Fox as Peri, as confirmed by his continued affectation of an American accent.
Despite the change in backstory, the plot of the serial remained essentially unchanged, including the significant incestuous subtext the series was calling upon at the time.
Unlike the TV Movie or The Day of the Doctor, Back to the Future has been repeatedly confirmed to be canon in Doctor Who. The Tenth Doctor informs Martha that time travel is exactly "like Back to the Future", and the series's continued and unabashed embrace of the Power of Love (something that would become common in many future stories) speaks volumes about the extent to which it touches the hearts of the creators. Bill even comes from Black to the Future.