No I mean playing 2 different games on different systems from the same account. Surely that's not violating anyone's EULA

From steams EULA:

"When you complete Steam's registration process, you create a Steam account ("Account"). Your Account may also include billing information you provide to us for the purchase of Subscriptions. You are solely responsible for all activity on your Account and for the security of your computer system. You may not reveal, share or otherwise allow others to use your password or Account. You agree that you are personally responsible for the use of your password and Account and for all of the communication and activity on Steam that results from use of your login name and password. You may not sell or charge others for the right to use your Account, or otherwise transfer your Account."

So unless you mean you are playing two different games by yourself at the same time, then it is in violation.

Are you serious? That is ridiculous. So when I buy a game off steam no one else in my household is allowed to play it?

This just reinforces my new found hatred for DRM.

Sorry, but that is not ridiculous in the least. Actually I conduct myself that way in every aspect of my life. For instance, we have three tv sets in our dining room, so we can make sure each one of us is staring at a different screen when watching films.
Unfortunately at one point we noticed that all 3 tvs were attached to the same dvd player, so in the spirit of not hurting the film industry we bought 2 more dvd players and now each tv comes with its own player.
Of course now we need to purchase 3 copies of every movie, and there is the trick of starting the 3 players at exactly the same second (because otherwise it all becomes a little confusing). But now I can proudly say that I live in a 100% pirate-free home.
Wait, I just realized that the three of us sit together in the same sofa. Oh cr*p...

This is not really an issue of DRM, but fair use. Several games on GOG have similar stipulations in their EULA, for example all EA games and Atari games (IIRC). The thought is that when you buy a game (or license) it is for your sole use, not communal.

DRM can be used to enforce this, though, but almost only to services like steam which require account sign-in.

Well you just have to switch Steam to offline mode on one computer and log into it on another.. You won't be able to play Steamworks titles via LAN, thou.

That is usual with every game retail, GOG,e tc. (as you only purchase a licence, and not a game). DRM is only enforcing the issue. Officially a GOG game can only be played by the person that purchased it, but the GOGs themselves have made clear that they don't mind you sharing it with your household.

Edit: typo

FAQ

9. Can I install one game both on my laptop and desktop PC at home?
Yes. We do not limit the number of installations or reinstallations, as long as you install your purchased games on PCs in your household. So yeah, if you've got a render-farm in the basement, you might actually break the world record for the number of legal Fallout installations in one household. However, if you think about installing your game on a friend's PC or sharing it with others then please don't do it, okay?

Please tell me this bullshit is just a f**king joke.

That, however, only talks about installations, not simultaneous players, or even letting others play your game at all. Whether by chance or conscious decision, I'll leave speculation to others.

As has been said though, they very much know and have acknowledged that they have no way to check (no DRM).

The T specifically said that it's ok for people to play on your PC while they're hanging at your household. The members of your household obviously spend a great deal of time hanging at your household and using the household machines. In their FAQ they specifically say that you are welcome to install the game in every machine in your household.

Technically a gray area it may be but in practical terms it seems pretty clear to me. Handing copies to friends or installing the game on PC's outside the household scope, those are definite no-no's and they specically tell folks not to do that. Installing the game on 2 or 3 PC's in your household so that you and the other members of your household can play them it's ok - my acessment, i dunno if anyhthing this specific was ever stated by anyone from gog. I'm pretty sure that if we're talking about two different games it falls in line with the parallel T outlined a while back between physicall and digital shinies and the so called 'wiggle room' - which is ok in gog's book. If the game happens to be the same, well, like i said, merely a technicality without any practical impact for gog or anyone else. Even if for legal or contractual reasons they can't flat out say it's ok i'm kinda leaning towards thinking they don't mind it - but again, this is my personnal acessment.

Please tell me you weren't born just yesterday.

Yeah, this happened to me too. I used to love Steam, because...well, hey, you can have all your games in one place without CDs! Now, after being on here for awhile, I'm like "yeah... I think I'll try to get my games somewhere else." I still use Steam, though, because otherwise how would I get my AvPC2K or Terraria fix?

I never tell f**king jokes, they're in very bad taste.

But it's a joke right? Please tell me it's a joke. If you have to, lie and say it's a joke.