Are there any plans to bring the Linux version to GOG ?

+1 for the Linux build.

As a backer of the first Kona, I would appreciate a Linux build too, but hey... :/

It shouldn't be rocket science... a Linux port exists, wrap it up with your fine GTK based Linux installer. On Linux these games basically just unpack to the specified location and run out of the directory, you really could just unpack a bloody tarball :-)

I have already purchased this just because I like to have things on GoG (and it works fine through translation) but I keep checking for a Linux installer for this game.

As far as I see a certain "pressurized platform" has the Linux build. It is listed there for Linux + their own distribution with system requirements by now.
*sigh* I really wish GOG would handle Linux builds better.