[UPDATE: Welcome, io9 readers! If you would like to learn more about this area, you should check out the Stanford Copyright & Fair Use Center.]

The sharp readers of io9, themselves a collective Library of Alexandria of science fiction, noted surprising common elements between James Cameron’s Avatar and a 1957 short story by Poul Anderson, "Call Me Joe:"

Like Avatar, Call Me Joe centers on a paraplegic — Ed Anglesey — who telepathically connects with an artificially created life form in order to explore a harsh planet (in this case, Jupiter). Anglesey, like Avatar‘s Jake Sully, revels in the freedom and strength of his artificial created body, battles predators on the surface of Jupiter, and gradually goes native as he spends more time connected to his artificial body.

James Cameron’s been here before. After foolishly telling the truth that elements of The Terminator had been inspired by two Harlan Ellison The Outer Limits episodes, Cameron was promptly sued:

Ellison filed suit against the studio claiming that THE TERMINATOR was plagiarized from his two teleplays for THE OUTER LIMITS. One was  "Soldier" (based on a short story he written years before), in which a soldier is zapped from a future war zone into the present and causes all sorts of problems. In addition to basic plot similarities, the scenes of the future in THE TERMINATOR are very similar in look and feel to those in "Soldier".

The other teleplay was "Demon With a Glass Hand", in which a lone man with a glass-and-computer-chips hand and a woman he meets up with are on the run from some unknown enemy. He has amnesia and doesn’t know a thing about who he is, or why he’s in his current situation. Eventually, he finds out that he’s from the future and was sent to the present on a mission to save the human race.

Cameron settled for an undisclosed amount. All versions of The Terminator distributed today include an acknowledgment to Ellison.

Of course, the paralyzed hero with a telepathic connection to extraterrestrials isn’t the entirety of Avatar, and, if Wikipedia is to be believed, "Call Me Joe" has none of the elements of colonialism, rebellion, spy-turned-double-agent and whatever else is going on in this epic helicopters vs. pterodactyls trailer.

Moreover, there’s nothing new about an author taking elements from pre-existing stories and re-working them. Ever see the play about the prince who feigns madness in response to his mother’s hasty marriage to a usurper and, after a complicated series of manipulations, kills a spy and himself?

No, not Hamlet. I’m talking about Vita Amlethi, written four-hundred years earlier by Saxo Grammaticus. (See the connection between "Amleth" and "Hamlet?")

If Shakespeare can do it, can James Cameron?

Probably so.

Let’s a take a peek at the filings in a lawsuit filed last year by the estate of the author of It Had To Be Murder (the basis for Hitchcock’s Rear Window) against Steven Spielberg, Dreamworks, and others over the movie Disturbia:

Steven Spielberg and major Hollywood studios stole the plot from Alfred Hitchcock’s classic 1954 film "Rear Window" in making last year’s "Disturbia," a lawsuit filed in Manhattan federal court on Monday said.

Dreamworks, its parent company Viacom Inc, and Universal Pictures, a unit of General Electric Co’s NBC Universal, are accused of copyright infringement and breach of contract for making "Disturbia" without first obtaining permission from the copyright holders, the suit said.

Spielberg, a Dreamworks founder, is named as a defendant. The film grossed about $80 million at the U.S. box office.

According to the lawsuit, filed by the Sheldon Abend Revocable Trust, the basis for Hitchcock’s 1954 film was "Murder from a Fixed Viewpoint," a short story by Cornell Woolrich.

Hitchcock and actor James Stewart obtained the motion picture rights to the story in 1953. The lawsuit argues that Dreamworks should have done the same.

"What the defendants have been unwilling to do openly, legitimately and legally, (they) have done surreptitiously, by their back-door use of the ‘Rear Window’ story without paying compensation," the lawsuit said.

As Spielberg’s motion for summary judgment argues,

"It is well settled that copyright law protects only plaintiffs particular expression of his ideas, not the ideas themselves." Arden, 908 F. Supp. at 1258; 17 U.S.C. § 102(b).7 As this principle is applied to literary works, general plot ideas of a work are not protected under the Copyright Act. Nichols v. Universal Pictures Corp., 45 F.2d 119, 122 (2d Cir. 1930)(a plaintiff can have no "monopoly" over a general plot idea); Arden, 908 F. Supp. at 1259-60 (generalized plot ideas are not protected, "even if first conceived by plaintiff’). …

Simply put, no one can own a general plot idea for a story. Davis, 547 F. Supp. at 726 (no protection for plot "about the Vietnam War and its effects on people’s lives, and … love triangles in which the betrayed member ofthe triangle commits suicide"); Giangrasso v. CBS, Inc., 534 F. Supp. 472,476 (E.D.N.Y. 1982) (plot ofa live radio broadcast from a remote location being interrupted by a man with a gun – not protectable); Midwood v. Paramount Picture Corp., 1981 WL 1373 at *1, *3 & *5 (S.D.N.Y. 1981) (plot idea of sheriff whose own posse and townspeople desert him and capitulate to outlaws, and sheriffs search for the outlaws -unprotectable); Berkic v. Crichton, 761 F.2d 1289,1293 (9th Cir. 1985) (plot of "criminal organizations that murder healthy young people, then remove and sell their vital organs to wealthy people in need of organ transplants" and "the adventures of a young professional who courageously investigates, and finally exposes, the criminal organization" – not protected because "[n]o one can own the basic idea for a story").

It seems Avatar might go down that road. If Anderson’s heirs can prove that the idea of telepathic control of an alien was entirely Anderson’s creation — which I doubt — then they might have a claim. The paralyzed hero is likely a wash; consider Rear Window.

It’d be better for everyone, and for art in general, if Cameron could simply acknowledge the inspiration, credit Anderson’s work, and thereby promote continued sales of Anderson’s work.

But that won’t happen without a lawsuit, not with what happened to Cameron last time he acknowledged inspiration.

Just one of the consequences of having courts of law, not courts of justice.