Hiya,

According to this post, Remastered Siege of Shadowdale has been added into the main game.
Is it already on GOG version of the game?

Jupp, checked yesterday and downloaded it.

Thanks for the reply :)

And how does it work? Because I don´t see a new module/DLC available on GOG, does the The NWN game connects to some server and downloads it from there? Or are they bundled in the game installer itself?

In the game itself, when you press "New" there is a tab called "Community" where you can download it and start a new save.
There's also a new version on the Neverwinter Vault that you can install manually, but this is easier and faster.
There are also a few other community modules there, I'm playing through the Aielund Saga and can recommend.

Perfect, this is the kind of answer I was hoping for - having it bundled with the installer :)
I am sure every single one of those curated contents are worth it, they were of the highest ranking longstanding mods even before EE.

Siege of Shadowdale was made by maestro mod maker Luke Scull. :) The original was his very first attempt at making a NWN mod, I believe (and it showed), but his skill improved leaps and bounds with each successive sequel. I haven't tried the Remastered version yet, but I'm sure it will be leagues better than the OG version and well worth the play.