Before the "modern" version of Evoland was released, there was free "classic" version. You can play it here via browser:
http://evoland.shirogames.com/classic

However, I would like to see an offline version as an extra. Few other games available on GOG also had free "classic" versions before their "modern" counterparts were released. Unlike Evoland, these games (in this case, Ittle Dew and Spelunky) have "classic" versions available for download.

I may have a part of an answer...

GoG can't do anything about it because an "offline" -nonbrowser version doesn't exist. The classic game was build in a language that, in some ways, uses Flash and so need a browser to be executed.

So maybe should you ask Shiro Games but I have a lot of doubts that they'll give you a positive response...


Naev.

Well... I'm pretty sure it's possible for a game to use Flash without running within a browser. I believe Machinarium does, which is why you lose your saves if you empty the Flash cache. However, I should imagine some repackaging would be required to convert a browser-based Flash game to non-browser-based.

It is very possible. The PC version of a little known game called Plants vs. Zombies is done in Flash. It is also possible to just have an .swf file on your computer, though at that point you are running it on your browser, just offline.