Never Say Never Again is actually a remake of the earlier James Bond movie Thunderball. It is considered an “unofficial” Bond movie because it was not produced by Albert “Cubby” Broccoli and was released by Sony, not MGM/UA.
By the late 1950s, author Ian Fleming had written seven books featuring James Bond, but had been thus far unsuccessful making a movie out of any of them. Hollywood was eager to make a series of movies involving the popular character, so they hired screenwriter Kevin McClory to work with Fleming to develop an original screenplay featuring James Bond. Together with another screenwriter named Jack Whittingham, they developed several ideas such as the villain Ernst Stavro Blofeld and the evil group SPECTRE, both had not appeared in the Bond novels thus far. They put together a completed story, but the deal fell through and Dr. No became the first Bond film instead.
In 1961, Ian Fleming adapted the completed story into his next novel, named Thunderball, but failed to acknowledge his co-developers. McClory sued Fleming for plagiarism and false attribution. The case was eventually settled out of court, with the result that all future editions of the novel should credit McClory and Whittingham for their contribution, and the assignment of the film rights to McClory. The film version of Thunderball was a result of collaboration between Kevin McClory and the regular Bond producers. One of the agreements stemming from this collaboration was that McClory would not make another movie using the Thunderball storyline until after 1975.
In 1976 McClory sued the Bond producers, stating that their continued use of Blofeld and SPECTRE infringed on the rights granted to him in the Thunderball settlement. MGM/UA argued that the settlement only granted him the rights to the Thunderball storyline, not the specific characters involved. The opening sequence of For Your Eyes Only, where Bond successfully kills Blofeld, is obviously meant as a dig at McClory, stating that they don’t need that character in order to be popular. When it started to look like he was going to lose, McClory withdrew the case. He then began production on his own Bond film.
When MGM/UA caught wind of the film, they sued McClory in an attempt to prevent it from getting made. McClory insisted that the movie was a remake of Thunderball and that he was within his rights. In the end, Never Say Never Again was released in 1983 with Sean Connery returning to the role of James Bond, 12 years after he said he would never play the character again. The “official” James Bond movie Octopussy was also released that same year.
In 1998 McClory again attempted to remake Thunderball, this time under the name Warhead. MGM/UA successfully prevented production, the court found that the new storyline strayed too far from the one originally established in Thunderball. Kevin McClory still maintains that the ideas for Blofeld, SPECTRE, the idea of using nuclear weapons for blackmail, and even “the film incarnation for James Bond himself” belong solely to him.
Sources:
http://www.mjnewton.demon.co.uk/bond/tb.htm
Danjaq LLC, et al. vs. Sony Corporation and Kevin O’Donovan McClory