Did you try running the Linux installer? As I said, I'm pretty sure it's just a shell script with binary data attached, so the installer should run despite the architecture difference.

Where do I find the Linux installer? When I click the games in my library, I only see Windows installers and very seldom Mac OS installer.

Some games have native Linux port, other doesn't.
On the Website, hoover the mouse on your name, click games and:

Edit: do not click the big blue button, it just install Galaxy. Below, there is the offline installers.

Just install your game on a windows pc, and look for the real game folder. For example, just checked on my own pc, under your DOOM 2 installion folder, there is another folder named "doom2", if you enter there, you can see the .wad file and original doom2.exe along with all files in the original dos version (I assume so). Just use dosbox to run this file and it should work. Note that the situation seems to vary from game to game, for example, Duke3D seems to have the original files directly in the installation folder. So you may need to check for yourself to make sure you are dealing with the right files. Hope this helps.

Rather than giving you advice for the PI, i'm just going to tell you how it got it to work for my android tablet, but slightly different. See, i run something called DOSBox Turbo on android. It works surprisingly well, but anyway...

First you need to get the stuff from the archives. The most reasonable way to do this is to install them on windows, then move over the installed files. What you do is you put everything into a folder viewable by dosbox. Now, the trouble is, most of these games need various configs that differ from game to game. For me, there's an app out there to help me manage these various settings. You need to figure this out for your copy of dosbox. I would start with some simpler games: things like dukenukem 3d and the like are going to be a royal pain. Some dos games aren't as difficult to run as others, but i honestly don't remember which are the easier ones to pick up and run. I'm not gonig to lie, you're probably going to have to post each game and ask people with what you have for help getting your copy to work for each game and how they have it set up. Vanilla dosbox loves config files to be passed via command lines, so i imagine that's the angle you'll be taking. This is not going to be a simple process, but that odesn't mean you shouldn't try. Just try to know how to reverse anything you do ,because, well, some people try things in the thick of things and end up getting lost in the process and create weird setups that no one knows how to fix.

Most probably will not help you, but try to use -g option. It set innoextract to handle archive as gog installer.

I.E. innoextract -g setup_dark_sun_shattered_lands_1.1_cs_\(28043\).exe

sounds like maybe your version of innoextract is too old. You need at least 1.8 or newer, iirc.
you can try and see if you distro has an update for a newer version available. But since you are probably running raspbian, the chances are pretty low as debian is usually not providing the latest version.

if you download the linux binaries from the innoextract homepage, it includes binaries for ARM that should work on raspberry pie.

I've downloaded about 10 games on my Windows machine and just copied them over to the Raspi. About two of them ran.

Has anyone ever tried Dosbian?

[url]https://cmaiolino.wordpress.com/dosbian[/url]

I think I might give this a try.
Ok thanks I'll try that out.

Keep up posted, please. This might be of interest to many, now or in the future.

Why do people bother giving advices while knowing fcuk all what they're talking about?

Because maybe the problem is too niche to expect anyone to be in the exact same boat, so comparison to similar problems might actaully be useful. Take my post for example: I haven't tried this with my pi, but what i did to apply it to android would apply similarly to how one does it for pi (especially as both are ARMs). Moreover, the general question is too vague, which shows a flawed assumption from the poster's point of view: each of these games requires complicated configs which aren't as trivial to move from the gog folder to your device. The OP needs to know what they're getting into, and how to approach it in a way more likely to get results.

Well the problem is not so much in it's being niche (it is ofc), so as the OP trying to launch the GOG installer expecting I've-no-idea-what on his Pi just means he has a long road ahead. And as 99% noobs do he starts about completely wrong on it. Good luck listening to dumb advice from windoze bums and the Linux noobz alike. Rather than invest an hour or two in actually knowing what you do.

Actually the problem starts with "why you even want such thing as playing dosbox games from a Pi, especially if you know f all about anything computer-related outside of the Start button"

But hey-hum. Hope he ends up trying to do something completely insane like installing wine on the Pi just to launch the installer or something. We're at the innoextract stage now it seems.

Obviously someone told hime it as a cool idea. Not a bad ideal, really, it's just this idea that DOS is simply an emulator like a NES emulator and the like seems to be where the problem is. If we were talking NES or anything similar, which is often suggested for pies, we wouldn't be having this conversation. The problem is, we're talking about the chaotic hardware mess that was DOS, special drivers for special hardware and all. It's pretty easy to see both where the problem is and where it came from, as well as how people get the messy idea that it would be easy. And, none of this has anything to do with one of the really annoying "non-bugs" of DOSBox with "long filename support." (Good luck running DJGPP, so hell if anyone will want to both investing in more solutions to the problem in the form of wrappers or anything, because it's a hard platform to bother with.)

Hmmm... you could install the game on windows, then copy the extracted files, and swap out the dosbox for the native ARM running one.

Though emulation IS going to slow it down. Expect 50-200x slowdown. Though depends on how it emulates it. qemu may be a better choice.

Regardless, after that, maybe a minor adjustment to the .conf file, though how much i can only speculate.

So when I start the games with the .conf files GOG provides, for example:

dosbox -conf dosbox_darksun.conf

I get some games to run with different results. Two games run flawlessly, but in Dark Sun for example there's no sound, some games have a CTD when I chose something from the menu.

At least a small step forward.

EDIT: I'm trying to figure out how the dosbox config files work. Does anyone know a good source of information?