The specs say it's required, and I don't see that it's multiplayer. Internet connectivity is not an option on my gaming machine, DRM issues aside, for performance reasons.

Internet connectivity is not an option on your gaming machine, then tell me how do you use GOG Galaxy Cloud service in order to upload your save files onto GOG Cloud without internet?

How do you buy and download your games from GOG Galaxy launcher in the first place, if you don't have internet on your gaming PC (offline PC)?

Do you think before commenting or you are just trolling?

Google what a usb stick is.

Since when do you have to use the Galaxy Downloader on GOG?

You can download the offline version at any time and it can be installed without Galaxy.

For example, I have never used Galaxy and probably never will, even though I use a lot of GOG games.

yeah, you can download the offline version of the game (setup file), but not from Gog/gog launcher directly. From sites that let you download the setup file for offline installation, yeah, but that's illegal, you don't buy for that game.

you can't download and use the offline version without gog galaxy, you need that app in order to buy and install the game with your account, if you download the offline version and never used Gog galaxy = mean that you don't buy a single game and you download all of them from torrent sites.

you install the game, works fine without gog galaxy no need internet for that, except, you don't have achievement and other features.

In order to install a GOG game legally, you need the gog galaxy app for pc/mac, then you buy the game and it will be added to your gog account, from the app, you can install and load the game and you google : "where to download gog games for free".

that's how you can download and install GOG games offline (from another pc with internet) and without using the gog galaxy app.

In other word man, he is getting the gog games for free, using another computer to download the offline setup file, then with an usb stick copy it to his gaming machine and install the game on his gaming rig.

He comes here asking for help for a game that he is not even own in a legal way, very smart idea.

You can download the game installer, patches and DLC's directly from the website.
And you don't need the GOG Galaxy app to install the game, patches or the DLC's.
Using the GOG Galaxy app is optional for most games on GOG.

Brother, do you even bother to check that you're correct before commenting, or are you just trolling?

Where do you think those sites get those files from? GOG automatically generates those installers and provides them for free, via the game entries on your account page on the website, or in the "Extras" tab on the game's listing in Galaxy. If you want to verify this for yourself, check the "Digital Signature" tab in the installer .exe's "Properties" - they are signed by GOG on generation, and this signature is hashed via SHA1 or SHA256 & cannot be spoofed. And there is nothing illegal about possessing these installers if you own the game - only distributing them if you have not purchased the game.

One of the biggest draws of GOG for those of us who care (which are more and more by the day) is the fact that they provide local installers for all games which do not require internet connections and therefore cannot be remotely changed or revoked at a whim by stores/devs/pubs (unlike Steam and others). That's what it means when you're said to actually own the games that you purchase on GOG - because you have complete control over and access to those installers that you download, forever. It's also why people like the user you replied to are so concerned about constant online requirements.

And if you don't understand why anyone would care about these things then all I can say is, maybe learn a little about this world you're living in before denigrating the choices that others make in living their lives.