Their FAQ is not really clear on that, my feeling looking at this page is that it is more like: this money goes directly in the pocket of GOG, so by helping us to generate more money for us, you are helping (indirectly) the preservation of games as it is what they do.
But I saw nowhere in the FAQ explicitly that this subscription money will only be used to the "active act" of preserving other games.
But I saw nowhere in the FAQ explicitly that this subscription money will only be used to the "active act" of preserving other games.