From the blue ones, so I think you should ask them for more info:

http://www.gog.com/en/wishlist/site/update_dosbox_and_scummvm_games_to_latest_versions

Read the comment posted on Jun. 5, 2012.

One point is that whenever a new DOSBox version is released, GOG would have to re-test (and possibly rewrite the conf files, if the DOSBox conf file format has changed yet again, like it has in the past) all their existing DOSBox games. Even for those games where the new version wouldn't offer any benefits. Lots of extra work for very little, if any (for most games), advantage.

Similar thing applies also to GOG's ScummVM games, ie. should they use only one ScummVM installation that all those GOG games utilize? There's an extra quirk that sometimes a new ScummVM version has broken savegames made with the earlier version, something that was pointed out in that same question.

What exactly would be the real benefits for using one common DOSBox installation for all GOG games?

- You would save a couple of megabytes of hard drive space per every GOG game that uses DOSBox.

- You would feel warm and fuzzy inside knowing you are using the latest version of DOSBox with all your GOG games, even if it didn't necessarily matter in practise.

- A few GOG games might even work a bit better with the newer DOSBox. But for these you can already now replace the GOG's installed version with a newer one, if it really matters.

Really worth all the extra work, trouble and risks? I would understand such practise better if GOG was the one controlling the development of DOSBox completely, because then they could control it themselves that shit would not hit the fan with some future DOSBox release.

Thank you, that's the first time I've seen it confirmed. Though T's in marketing, so he isn't really the person to ask.
Efficiency. Plus, I believe ScummVM can be set up as a client of sorts, so you can add more games to its user interface and launch them from there. It just seems like a reasonable thing to do, that's all.

Please note I'm not saying GOG should implement it. I just think it's an idea worth considering.

(By the way, there's been almost a full year between the releases of DOSBox 0.73 and 0.74 and the relationship between GOG and the DOSBox team is known to be very friendly. So I think worrying about sudden changes in compatibility is a little extreme.)

(Also, DOSBox 0.74 is two years and five months old.)