Almost a century after his big-screen debut, Mickey Mouse enters the public domain Monday, opening the floodgates to potential remakes, spin-offs, adaptations… and legal battles with Disney.

The copyright on "Steamboat Willie" — a short, black-and-white 1928 animation that first introduced audiences to the mischievous rodent who would become emblematic of American pop culture — expires after 95 years, on January 1, under US law.

The date has loomed large on the calendars of everyone from filmmakers, fans, and intellectual property lawyers to Disney executives, who in the past helped lobby to change the law to prolong US copyright terms.

"This is a deeply symbolic, highly anticipated moment," said Jennifer Jenkins, director of the Duke Center for the Study of the Public Domain. 

Anyone is now free to copy, share, reuse, and adapt "Steamboat Willie" and "Plane Crazy" — another 1928 Disney animation — and the early versions of the characters that appear within them, including Mickey and Minnie.

A vital caveat is that later versions of the characters, like those in the 1940 film "Fantasia," are not in the public domain, and cannot be copied without a visit from Disney's lawyers.

But artists would be free, for instance, to create a "climate change awareness version" of "Steamboat Willie" in which Mickey's ship runs aground on a dry riverbed, or a feminist retelling where Minnie takes the wheel, said Jenkins.

That would echo imaginative re-uses of other characters whose copyrights recently expired such as Sherlock Holmes and Winnie-the-Pooh.

Legal skirmishes

But it will not be plain sailing.

In a statement to AFP, Disney said it would "continue to protect our rights in the more modern versions of Mickey Mouse and other works that remain subject to copyright."

Indeed, the version of Mickey in "Steamboat Willie" is a spindly, roguish creature who would not be recognizable to many younger viewers.

"What's in the public domain is kind of a frightful little black-and-white animal," said Justin Hughes, a professor at Loyola Law School.

He added: "The Mickey Mouse that is most familiar to current generations of Americans will remain under copyright protection. 

"I wouldn't be surprised if we see some legal skirmishes, and I wouldn't be surprised if we see Disney out there educating people on that point."

Cease-and-desist letters could be sent to artists producing "high-budget fan art" if they use elements from later Mickey cartoons, such as red shorts and white gloves, he predicted.

Additionally, while the copyright has expired, the trademark has not.

Copyrights prevent the unlicensed copying of the creative work itself, for example, books, films, and characters. They expire after a set time.

Trademarks guard the source of work, preventing anyone else from making a product that could mislead consumers into thinking it came from the original author. They can be renewed indefinitely.

Disney said it will "work to safeguard against consumer confusion caused by unauthorized uses of Mickey and our other iconic characters."

The company has even added a clip from "Steamboat Willie" to the opening sequence of every Walt Disney Animation Studios film.

"They were very smart folks at Disney — they realized that the best thing to do was to establish that iconic sequence of Steamboat Willie as a trademark," said Hughes.

Anybody using the classic image of Mickey at the helm of the boat on shirts, caps, or mugs could be open to legal action, he said.

Circumvent

Other experts such as Jenkins remain more bullish about public domain freedoms.

"Our Supreme Court has made clear that you can't use trademark rights to circumvent what copyright expiration allows," she said.

Both sides agree that the law is likely to be tested in court soon.

Anyone hoping to cash in on Disney's beloved mascot "should move cautiously and with counsel," added Hughes.

In the short term, novelty and shocking adaptations, similar to the recent high-profile slasher film "Winnie-the-Pooh: Blood and Honey," are likely to grab the headlines.

But copyright law should ensure artists can use characters like Mickey to create enduring works, just as Shakespeare has been adapted to make modern classics from "West Side Story" (a retelling of "Romeo and Juliet") to "Rosencrantz and Guildenstern Are Dead," (Tom Stoppard's exploration of the fates of two minor characters from "Hamlet"), said Jenkins.

"I'm interested to see what happens in 2024," she said.

"But I'm even more interested to see what we're still talking about and thinking about and teaching and writing about and sharing with our children in 2054."