In highly unusual move, Nintendo targets a ROM hack—essentially, a mod.

https://youtu.be/Y9uP_Hpn8U8

A fan-made Pokémon ROM hack in the works for eight years was set to launch this Sunday. But a letter sent by Nintendo's Australian law firm on Wednesday has stopped those plans in their tracks.

According to Adam "Koolboyman" Vierra, developer of the fan-made Pokémon Prism project, Nintendo's Australian law firm sent him a cease-and-desist letter, which he uploaded to Google Drive with identifying information redacted. (American representatives for Nintendo were not able to confirm the letter's authenticity as of press time.) The request alleges that Koolboyman's project, which alters the source ROM of the 1999 game Pokémon Gold to create an entirely new adventure, violates multiple Australian laws.

Even though Vierra's public profile says he lives near San Francisco and Nintendo has headquarters and legal firms in America, Vierra clarified on his Twitter account that the game's planned launch site, Rijon.com, is hosted in Australia. Nintendo's Australian law firm, Addisons, has taken action against downloaders of commercial Nintendo products before, but the firm appears to have done little to nothing about makers of Nintendo-infringing software.

Other recent Nintendo takedown notices, like the one sent to a fan-made remake of Metroid 2: Return of Samus, have come in the form of DMCA notices. These legally questionable projects have typically been made from scratch, with game assets and art being extracted or recreated by the creators and then slapped into other game engines.

Pokémon Prism is different because it's a "ROM hack"—meaning, it's not a full game. Rather, Prism is a small patch file that is worthless without the original ROM file (which can either be legally dumped from a cartridge or maybe-not-so-legally downloaded from the Internet). Computer gaming fans would describe this kind of release as a "mod." Mods do a similar thing: they take existing, paid-for game engines and assets, and they apply a patch file that remixes existing content and adds new twists.

Mods typically launch for free to avoid the most obvious legal issue that might arise from commercialization. Pokémon Prism would have launched as a free patch file download, with no links to Pokémon ROMs, as well.

Legal action has rarely been taken against such mods in the United States, with the exception of mods that have inserted other IP holders' content into games without their consent. Perhaps the most famous mod of them all is Counter-Strike, a Half-Life mod that was so successful, its creators were hired by Half-Life's creators in order to release the mod officially as a standalone game.

Nintendo's history of legal challenges to anyone toying with its IP is long and storied. However, Nintendo fans may be surprised to learn that the company does not have a history of taking legal action against fan-made ROM hacks. The most famous of these is an English-language translation patch for the Japan-only Game Boy Advance game Mother 3. You can still download that hack really, really easily, and it's been hosted at the same site since 2008. That game's American prequel, Earthbound, remains a cult favorite, and the series' English-speaking fans have also published fan guides about Mother 3 without facing legal action from Nintendo.

Additionally, giant online fan communities have formed around ROM-hacked versions of older Super Mario games, which mostly exist to make absurdly difficult versions of the games' classic levels. Instead of issuing C&D letters to the makers of these hacks, Nintendo has aimed its legal crosshairs at YouTube streamers who play these ROM-hacked Mario games. (Other similar Mario-related hacks have been written about at Ars.)
Vierra himself might have assumed Nintendo would allow a Pokémon ROM hack, because his last one, Pokémon Brown, launched in 2004 with nothing in the way of dispute from Nintendo. That hack's new "Rijon" region would have been hugely expanded upon in Pokémon Prism. It would have contained other tweaks, such as Brown's special monster types (wood, gas, wind, abnormal, and sound), a tweak to the game's "clock" system, and new music compositions. (Other Pokémon ROM hack depositories are easy to find online.)

"Nintendo understands that you are a fan of its original products and its Pokémon franchise," the letter to Vierra reads. "Whilst this is appreciated, it unfortunately does not alter Nintendo's important role to ensure that all of its valuable IP is fully protected and that there is no use made of any of its intellectual property rights without proper supervision and authorization."

Vierra responded on his Twitter account by blaming himself for attracting attention to the patch close to its release date. "I'm also responsible for this situation," he wrote. "Trailer shouldn't have been made & I shouldn't have been such a perfectionist and finish it sooner [sic]." Near-final footage of the game was streamed at the popular Twitch Plays Pokémon channel in October.

Vierra declared the project "cancelled." He did not indicate whether he would consider other plans for releasing the ROM hack.