I think it's because players have to download an old version of WoW in order to play. This is a full game download and includes artwork and music IP content. Not to mention it means there is no need to pay a monthly fee to Blizzard.
Blizzard is fully in their right to shut it down, but it's unfortunate the current state of things.
This is not about getting around paying for WoW. Vanilla WoW is practically abandoned-ware. Blizzard has been clear they have no plans to launch a Vanilla server, and they don't even seem sympathetic to the idea. There is content and gameplay in Vanilla that you cannot experience in the current version of WoW. There are many old school players who have fond memories of Vanilla (including me), and we have no way to get our nostalgia fix other than a server like Nostalrius.
I have moved on from WoW and have no interest in the current game, but I would enjoy experiencing Vanilla again, just like I enjoy playing old SNES RPGs, listening to 80's music, or reading the same books or watching the same movies over and over. With other forms of media you can do that, but not here. I understand the legal reasons, but still, it's unfortunate.
I see this as another new and lamentable consequence of things moving to the cloud. I find similarities here with the Nest/Google fiasco. It used to be you could buy something and it was yours, completely, forever, to do with whatever you want. Now, not as much.
The problem legally is Blizzard is going to have an extremely hard time proving a private server user downloaded an unauthorized copy of WoW from a third party rather than from Blizzard themselves when the version they are playing was the live version.
There are a lot of nuanced stipulations involving the legal distribution of the Wow client:
* The game has always been distributed using peer to peer seeding, such that Blizzard has never been the exclusive provider of game data, they just told users where to get the data from.
* Blizzard has in several cases (mostly early on) recommended users download whole copies of the game from third party websites like fileplanet back in the day when the servers were overloaded with players updating to new versions of the game.
* Blizzard has always made WoW available as freeware, and has never auth-gated the download pages before the Battle.net launcher. Old versions of the game used to have installers hosted on Worldofwarcraft.com that anyone could download with a URL regardless of being signed in or not, and users could make accounts without buying the game anyway.
This isn't some classical "game developer sells copies for money and people were sharing copies without permission". Today, anyone sharing WoW clients through torrents is obviously violating blizzard IP, but the distribution methods of the client in the past, combined with the fact no player needed to have an account or paper trail showing they had a legit "claim" to the game to have the client, means they cannot realistically argue that anyone playing a private server also violated their copyright on the client. They could have easily obtained it legally, and just changed the home server to a private one so it never updated. That is a violation of the ToS in the game, but not an IP violation, and ToS are civil matters that are often not even upheld in court when tested, and WoW has a fairly grandiose ToS if it were ever put in a real trial.
Legally they might be within their right, but cases like this really demonstrate to me that there ought to be some legal concept of abandonware when a product is substantially modified from its original state.
What precedent does it set that you have no legal right to retain access to software in the form that you've paid for it? If Gabe Newell went insane tomorrow and fired all employees then shipped patches making all Valve titles unplayable is there really no legal recourse for the people who bought those games? This is a case of the law being behind the technological realities in my opinion.
(and yes I know there's probably some EULA cop-out about how you don't own the client and merely paid for a temporary license to it or blah blah blah)
Library of Congress did change DCMA rules last year to allow consumers to modify an abandon-ware game to bypass authentication servers that no longer exist. However, they specifically excluded MMO-like games, only covering "video games that can be played by users without accessing or reproducing copyrightable content stored or previously stored on an external computer server". Still, it's at least acknowledgement that abandon-ware is a legitimate form of media that rightfully deserves preservation.
It also doesn't allow for copying of games beyond personal use as I understand it, so it's really hitting MMO emulation from two directions as it's currently defined. How many of your potential players still retain the original install disks, especially after 12+ years? I can't imagine very many.
Blizzard is fully in their right to shut it down, but it's unfortunate the current state of things.
This is not about getting around paying for WoW. Vanilla WoW is practically abandoned-ware. Blizzard has been clear they have no plans to launch a Vanilla server, and they don't even seem sympathetic to the idea. There is content and gameplay in Vanilla that you cannot experience in the current version of WoW. There are many old school players who have fond memories of Vanilla (including me), and we have no way to get our nostalgia fix other than a server like Nostalrius.
I have moved on from WoW and have no interest in the current game, but I would enjoy experiencing Vanilla again, just like I enjoy playing old SNES RPGs, listening to 80's music, or reading the same books or watching the same movies over and over. With other forms of media you can do that, but not here. I understand the legal reasons, but still, it's unfortunate.
I see this as another new and lamentable consequence of things moving to the cloud. I find similarities here with the Nest/Google fiasco. It used to be you could buy something and it was yours, completely, forever, to do with whatever you want. Now, not as much.