I am personally very excited for AppImages! So far it's the fastest and easiest way to run third party applications that are not available in the distribution repositories. And it (more or less) works across all distributions.

It is different from Mac .dmg, though. The content of a .dmg file is an .app bundle that user moves to the Applications folder on user's Mac (which is something similar to Program Files folder on Windows). That way the application is installed locally in a officially supported path.

Instead of that, AppImage uncompresses the application on each run, which might make the application start considerably slower. This acts like portable applications known from Windows:
http://portableapps.com/about/what_is_a_portable_app This is sadly a problem that AppImage doesn't solve and also a reason why we chose to use an installer that is started via a shell script.

Btw Shots fired! :)

No serious benchmarks, but with a timer, AppImages were considerably (a few seconds) slower. Using regular SATA hard drive, not a SSD.

Is ext4 modern? :)

If the game needs extra dependencies we always put that information in the system requirements field of the game, see here for Little Inferno:
https://www.gog.com/game/little_inferno

That solution is obviously far from perfection (as we use only names of Ubuntu packages, and it puts a bit of extra effort on the user).

The problem is, Linux is still fresh grounds for many game developers and often they don't know they can satisfy dependencies by putting needed libraries in the game folder or that they should produce a 64 bit binary. And what to do about old games, that were compiled years ago only with 32 bit in mind? Or with game engines that don't offer 64 bit support, such as Game Maker?

And shipping the libraries with the game by GOG might sometimes prove problematic, as it causes compatibility issues (that's why we stopped doing so for some time already).

There are situations where you cannot avoid installing extra dependencies on the user's side. We are actively investigating possible ways of fixing that problem.

RE: AppImages

As many of you noticed, AppImages have their own disadvantages.

I believe they are not suitable for shipping games, at least not in the current shape and surely not for DOSBox or Wine titles, or any other games that require ability to write files in the game folder.

We're gonna stick with installers in the foreseeable future.

Well, to be honest, if the games followed "the Linux way" of doing things, all configs and saves should land up somewhere in ~/.config or ~/.local/share . The gamedevs often don't know about it, but it's ok, Linux is still new grounds for many.

Making game assets accessible for modding purposes is of course a separate matter :)