C'mon GOG, what's the idea of locking this behind the requirement to own the base game here on GOG? I already own it on Steam and have the original disc, and just want the added benefit of having this here on GOG which I know and trust. Anyway, I've simply gone to their own website where they are offering the download free to all with no hidden restrictions. Bit silly on GOG's part really.

My guess is that the download on GOG has some of Oblivion's files included in its installer so it needs to be sold like this otherwise you'd be able to download at least parts of Oblivion when you downloaded Nehrim: At Fate's Edge from GOG without owning Oblivion.

That is why the system requirements say: