quixotecoyote: I have the base Tropico 4 from Steam. I remember having problems getting DLC from other sources to play nicely with it. Can anyone confirm whether it's possible to use this DLC with that version?
I doubt it would work, because for example Steam's folder structure is different and also because the DLC installer is explicitly looking for the installation of the GOG version. But more importantly, you can't buy and download the DLC on GOG without owning the base game. You can buy a gift code though, but only somebody owning the base game is able to redeem it and add it to his/her library.