I'm really surprised that GOG hasn't snagged Majesty Gold yet. As far as I know, it's already available for Linux, PC, and Mac, so it should be an easy game to add.

a game only needs to be compatible with windows to be on gog
it has more to do with whoever owns the rights to the game and whether or not they want to provide it on gog

GOG isn't exactly Mac and Linux friendly, so that doesn't matter.

Majesty is on Impulse though, how did they get it?

Impulse is bigger than GOG by a ton.

Additionally, Impulse allows for game to have DRM, even though Stardock is philosophically opposed to DRM. GOG is specifically DRM free, which can be a sticking point for many of these publishers.

Ubisoft is up there with the list of other mega-publishers though, and they're willing to give GOG a shot. I guarantee that the other publishers are watching.
I believe it was stated in an article on Ars Technica that GOG was getting a 'trial run' from Ubisoft (though it was not explicitly stated that way) and were getting a few titles from their back catalog to see how well they perform.
I'm guessing it it's shown to be worthwhile, they'll start releasing even more games. If they do, other big publishers might start following suit. I'd expect EA to be one of the last, but who knows? If they want to get back in the good graces of a lot of PC gamers, then joining up with GOG would be one big step.
I do think, however, at least one other big publisher joining, be it EA, Atari, or heaven forbid, LucasArts, the others will be quick to follow suit. They go where the money is. Good favor from their consumers never hurts either.

The problem with these big companies though is, as other people have pointed out "DRM free."
The big companies have this retarded illusion that DRM works and at least slows the piracy down to an "acceptable" level. (basically like how supermarkets have to account for certain losses to shoplifting)
So, in their mind .. DRM free is like.. well... I could put the Fallout, Fallout 2 and Fallout tactics installers on a DVD, make a dozen copies of that DVD, and pass it out to everyone I felt like. There would be no way to tell it had been done from outside of the circle of those receiving them. Big companies don't like the idea of that happening with their products. One person buys it, 50 people get it.

Oy vey... why does every thread here gets hijacked into a we-hate-DRM thread?

The Majesty-brand is owned by Paradox Interactive, and they're selling Majesty Gold on several portals as well as in retail stores. I'm sure Paradox will sign up for GOG eventually, but the fact that they own the Gamersgate portal (which is, after all, competing with GOG) probably means they're not in a hurry..

Uh.. this hasn't
Maybe a "We hate big companies who think DRMs are better than sex." thread.. But my opinion on DRM in no way shape or form effected what I expressed.
I expressed, in simple terms:
Big companies want to ensure their product is not illegally distributed. They use DRMs for that. GOG is DRM free. So, Big Companies don't think partnering with GOG is in their best interest business wise.
(Penny wise, pound foolish, as the saying goes.)
I'm one of the LAST people who'll turn a thread in to a "I hate DRM" thread. Because.. I don't hate DRM, I don't have anything against reasonable DRM.

I HATE DRM!

Speaking of that, how is Gamersgate? Anyone dealt with these people before?

It's basically the retail disc given to you through the tubes. All that nasty SecuROM stuff is still there.