Weeks after forcing the shutdown of a popular, fan-run "pirate" server that ran a classic version of World of Warcraft, Blizzard now says it basically had no choice but to go after Nostalrius to protect its legal rights.
"Why not just let Nostalrius continue the way it was? The honest answer is, failure to protect against intellectual property infringement would damage Blizzard’s rights," World of Warcraft Executive Producer and Vice President J. Allen Brack writes in a post on the official WoW forums. "This applies to anything that uses WoW’s IP, including unofficial servers. And while we’ve looked into the possibility—there is not a clear legal path to protect Blizzard’s IP and grant an operating license to a pirate server."
In the narrowest sense, Blizzard's copyright wouldn't suddenly be invalidated if the company decided to look the other way for one popular "vanilla" server; you can't lose a copyright just by failing to defend it legally. Still, failure to go after Nostalrius would have done some damage to the idea that Blizzard is in full control of the World of Warcraft IP and could have encouraged others to think that such unofficial servers were OK. Even now, there are plenty of other pirate servers out there running previous, current, and/or modified versions of World of Warcraft, most of which have yet to draw Blizzard's legal fire.