Does the version they sell on GOG.com include the following DLCs ?

-Deceits,
-Blight of the Bogs
-Wraiths of the Quiet Hamlet
-Wedding
-Merry Witchmas

I'm asking this because the Director's Cut on Steam doesn't come with those 5 extra DLCs and I had to install them manually.

GOG has the 1.5 Patch and these are in that patch. From the installed GOG Witcher Readme

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4. New features and fixes
======================================================

The package updates the Witcher to version 1.5 and brings following changes:
- Adds fixes included in patch related to EAX problems.
- Removes copy protection (DRM). Game no longer requires game disc inserted in DVD-ROM in order to play. This refers also to D’jinni Editor.
- Patch includes 5 fan made adventures: “"Blight of the Bogs", "The Wedding", "Merry Witchmas", "Wraiths of Quiet Hamlet", "Deceits". All adventures are translated to English and Polish, and only have subtitles (no voices).

Alright, thanks for the clarification.