Nordlandtrilogie Forum

I will forward your question to the DEVs. Technically, it should be possible, because the game was sold as a boxed version, too.

Also GOG usually insist on using their own installer... so their releases are usually late

As far as I know a GOG release is planned later (at least thats my last information), although we are talking more like weeks, not days like the patches at the moment.