Grargar: Maybe Arcania, as ShinyLoot was the only digital store that sold it DRM-Free. Oh sure, I know that GOG has rejected it, but maybe when Nordic drops its price, they could reconsider it.
For the maingame Gamersgate offers a patch that removes the Securom DRM (ArcaniA_Gothic4_Patch_Sec_Installer_EFIGS.exe). In my textfile I create for every series to collect any relevant informations I also wrote you need to install an offline-installer before installing the patch, because the patch does not removes the first validation. I guess the offline is the second downloadable patch (ArcaniA_Gothic4_Patch_Installer_EFIGS.exe).
About the standalone addon "Fall to Setarrif" I'm not sure. I remember it was and there is no activation code, but the gamepage says it has Securom. I never played both games, I got them by mistake as free upgrade to the Gothic bundle, so I can't give any guarantee for both ;-)
Edit: And yes, it would be great to get more games activated here from other stores, especially when they are already gone like ShinyLoot. While I had some games on ShinyLoot (and of course backuped) I believe none of them are on gog.