Again, there are 2 ways a game can be using a CD-key for multiplayer.
Method 1) is like Unreal Tournament, which used it as a copy protection, since some (not all) servers only allowed one instance of a CD-key to be connected at the same time. If your server didn't have that restriction, you could have 16 players playing with the same CD-key (fun times at the Computer Lab classes in the university).
Method 2) is like HoMM V, which uses the CD-key as an identifier, akin to your computer's ip address. While you can play single player without problems, if you try to play multiplayer with two or more instances using the same key, the server cannot communicate effectively to any of the players.
So, a CD-key can be used as a copy protection scheme, it can also be used as a network identifier, or it can be used as both. Depending on implementation, a CD-key may no longer be required, in which case GOG.com removes it (see, again, UT).
If you don't mind me asking, what games were you able to play using one cd-key for every player?

and yuou forget it my friend. LOL I can`t Lie is part of it(I have 2 copies on them I explain it) X3

Thaks for the explain my friend. realy clear. I know there is not solution Legal then this game can go to the hell and ubisoft too... X3

and if you help us say us what games has no restriction copy in your own blood. I will really thankfull.

I think two users in the same family should be able to play the game multiplayer. Why should you have to buy two copies to play the game in one household?

Yep, you should have bought another copy when it was $7.99. You can't use the same multi-player code at the same time on two machines.

For the same reason those 2 computers need to have different IPs (even if internal IPs). So the network code doesn't conflict. Read post 16.

Well, maybe you should be able to request additional keys. A household should be entitled to play a purchased game IMHO.

I think the pro-DRM trolls do have a point that the CD-keys, which in any way restrict one to use one copy of the game to play multiplayer game online against each other, can be considered as a form of DRM. Depends partly how you define DRM, like in some earlier DRM discussions people have said that it is "DRM" only if you need to authenticate the game online with some central game authentication server (in which case this is not DRM, but something else). For example, to them CD copy protection is not a form of DRM, even though its sole purpose is to restrict several people from playing the same purchased copy of a game simultaneously on several machines.

It depends what you are looking for with the lack of DRM. For me personally, it is for allowing me to install and play the game independently of the publisher, without having to rely on any publisher server (which might become permanently offline at some point, a bit like the Rise of Legends update servers) to grant me access to the game. Even if the publisher and their authentication servers are long gone, I can still play these games' multiplayer, even if not using one copy with all my friends. But I can play multiplayer against their own purchased copies of the game, without the presence of the publisher and their servers.

To me it is similar as some old (GOG?) games that may still have manual keyword checks. Is that a form of DRM, or not? Irrelevant to me, as it doesn't restrict me from playing the game without the presence of the publisher or IP holder. I can still play the game independently of them.

But if you are looking for being able to share and pirate one purchased copy of a multiplayer game around with your friends, then this CD-key thing definitely becomes an unwanted restriction, a bit akin to DRM. I guess GOG just needs to be clearer in the game cards when such multiplayer restrictions exist.

And yes, "DRM free" is definitely a marketing term, just like "good service", "cheap prices", "fast delivery" etc. Being also a marketing term doesn't make it useless from the user point of view, though.

They are. Just not multiple instances of the same copy at the same time.

You are. For a small fee of $5.99 to $29.99, depending on what kind of key you are looking for ($29.99 for Arma 2).

You know what I meant. I guess people affected will have to pirate the extra copies. Great way to encourage legitimate consumption, DRM.

When you buy a game that requires a unique multiplayer cd-key, you are actually given 2 keys. One is the generic used in the single player, and the second is the unique one you are given by support. Depending on method used, you may be able to use those 2 to play.
As for requesting an extra cd-key, that does mean you are requesting an extra copy of the game. What prevents me from asking for 5 extra copies (2 for my parents, 3 for my siblings), then trading those copies?
So no, it's not DRM here, it's retarded network code. And I'm not sure you'd be able to play with a pirated copy, though a keygen may (or may not) help.

The same thing that keeps you from going to <torrent site.com> and entering "GOG.com" into the search field.