One of the most popular "pirate" servers for World of Warcraft, running a classic version of the game no longer offered by Blizzard, will be shutting down under the threat of legal action from Blizzard.

The Nostalrius servers had been in operation for about a year, running version 1.12 of the original World of Warcraft as it existed in 2006, just before the release of "the Burning Crusade" expansion. The administrators say that 800,000 registered accounts and 150,000 active players were working through quest progressions reproduced to precisely match the game of a decade ago.

But the team behind Nostalrius says its French hosting provider has been issued a formal letter asking it to shut down the servers or face a potential copyright infringement lawsuit. As such, the servers will be shut down on April 10.

Hosting private servers is explicitly against Blizzard's Terms of Use, a rule the company says "isn’t an issue because of ‘lost’ subscription fees from players choosing these illegitimate servers over the real WoW servers—it simply boils down to the fact that private servers are illegal, and that’s that." Yet despite the legal threats against Nostalrius, there are still dozens of other active private servers offering various historical, current, and modified versions of the game. A Blizzard representative was not immediately available to respond to a request for comment.

In an open petition to Blizzard, the volunteer team behind Nostalrius said its efforts came our of a passionate fandom for the game and weren't intended as a way to subvert Blizzard's World of Warcraft business. "We never saw our community as a threat for Blizzard," the petition reads. "It sounds more like a transverse place where players can continue to enjoy old World of Warcraft's games no longer available, maybe until a new expansion appears." As of this writing, nearly 25,000 people have signed the open letter "in hopes that changes may be made possible in the link between Blizzard and volunteer based legacy servers."

Though Nostalrius is going away, the team says it "will still be publicly providing everything needed in order to setup your own 'Nostalrius' if you are willing to." That includes source code and anonymized player data that can form the basis for a new Nostalrius-style server hosted somewhere else. "We will still be there in the background if you want us to, but will no longer take the lead... Today is also the day where Nostalrius will start being community-driven in the truest sense of the word."

Preserving the original experience of constantly changing online games is a persistent challenge for gaming historians and preservationists who struggle to maintain the context and ephemera around a game's living history. The Internet Archive's Jason Scott suggested to Ars that a Nostalrius-style server could serve as a kind of "colonial village model [of preservation], where you hire people to walk around like 1990s assholes."

"We might eventually see people whose job is to play older games and speak in language that is accurate to the period and use techniques that were popular then to take you on," he said. "I don't think that's that farfetched an idea... not for something that has had such an impact... where a person could play an older version of Warcraft with people who are in their 40s and 50s as they used to play it in their teens."