I know that a lot of game companies are afraid of using non-DRM, but there are many people out there who will (and do) buy and support software that is DRM-free. GOG.COM is second only to Steam in internet sales. While you might be a little worried about releasing the game to GOG, I would recommend at least releasing the first UFO ET game to GOG to see how well it does. I imagine you are not selling a whole lot of UFO ET 1 right now, so it can't hurt and you may find that there is a good fan base that supports DRM free games.
In short, is there any chance that the game will be distributed on GOG? Will you release the first game on GOG? What distribution are you planning on having? So far it looks like I would have to order it from Europe (through your company).
Thanks