P1na: An open server distributed with the game, perhaps?
That way, even if the official servers fall, you could still play the game through fansite servers or alone with just your friends. Or single player, even.
MarioFanaticXV: But even the private/fan servers would still have their own DRM, no? You'd still have to log into those servers is what I'm saying, and that would require an account log in.
As long as you can use the product in its full capacity at any time you want, there's no DRM. Restrictions imposed on you by private servers would not be DRM since they're not restrictions imposed on you by the product, but by other users. You can host your own servers and use the product to its full capacity with your own rules.
Say I host a game of Terraria, but I only want to play with my friends, so I set a password. If you're not my friend, you don't get to join. Is that DRM? No, of course not. It's my server and I can play with whoever I want. Even though you can't play on my server, you can play on your own server.
Say I host a server without a password and advertise it online. I tell everyone that they're free to join but their characters are not allowed to wear hats or helmets while on my server. I kick and ban players who break my rule. Is that DRM? No, it's my server. If you don't like my rules, you can play on your own server.
Say you're concerned about players cheating. You don't want to be worried about players editing their save files and flooding the game with rare items. So the game makes all characters be stored server-side, and you have to log in to the server to access your character. Is that DRM? It's more complicated, but the answer is still No. Why? Because you still have access to all of the game's functions. By playing on my server, you entrust your character's save file to me, and the worst that can happen is that you lose access to that save file. Your game still retains full functionality. If you don't like this risk, you can play on your own server.
Now, just because it's DRM-free doesn't necessarily make it a good idea as a purchase. Playing an MMO on your own might not appeal to many people. So even though the game is DRM-free, you might only buy it because the publisher is still hosting their official servers. Once those servers go down, there might not be any unofficial servers big enough to give you a good experience, or with enough rules and protections to prevent cheating. But that's another matter altogether. The lack of good servers might defeat the point of playing an MMO for you, but all that's required for the game to be DRM-free is for you to be able to play it fully from your offline box. And all that requires is that you can host your own server.