I am a GOG.com user since 2011, bought and own 300 games on GOG (I have 30 on Steam) and would have bought way more if I wasn't poor as hell for years now, hate DRM and Steam with a passion and advocate GOG over Steam everywhere I go.
Yes we on the TTW team want to screw GOG.com purchasers!
First of all, the mod checks for genuine versions of both games, this has nothing to do with checking DRM.
Second this mod was started almost 5 years ago and it is a continuation of a much older mod. Back then there was no GOG.com selling the games.
Third, the GOG.com games only just now (almost literally just now as in less than a day) became available while our latest installer is almost two years old. So how would it be able to recognize as genuine a version of the game that only exists 2 years after it was programmed.
Fourth, be assured that we on the TTW team want what we always want, provide a free and quality product for anyone with genuine versions of the games. I am sure our next release should already come with an installer that will recognize the GOG versions.
Fifth, remember to breathe and calm down, no one is waging war on gog costumers anywhere as I can see (being one of them for almost 8 years myself like I said).
Sixth, as to answer why we check for genuine game versions, it is because if we allowed pirate versions of the game to easily run TTW, Bethesda could have legal terms to come by and shut us down (as in, accepting and/or encouraging piracy of their games or something silly like that). We rather not have legal problems with Bethesda because we love what we do and we would close shop if they told us to do it.
We will need to have access to the GOG.com games to study them to see what differences from all the other genuine versions are in them and then have our Installer recognize them. This will take a while and will cost money since someone on the team will have to buy the games on GOG.com to do this. Then we will have to program the installer. This will take work, money and time spent by people who are doing this for free and on our free time.
So to sum it all up:
No one is out to get GOG.com customers. 