Due to a situation beyond their control GOG.com has been forced to remove Fallout, Fallout 2, and Fallout Tactics from sale. The games had been available since the site launched five years ago so this is a huge removal.
If you have already purchased any of those games from the site you can still download them from the My Games section.If you received a gift code for any of those games in any giveaways you’re out of luck as the codes are no longer valid. However, if you bought a code for any of the games that weren’t part of the giveaway then you can still redeem them.
Until any party involved comments more on the situation there can only be speculation as to why the games were removed. One could be that the license agreement ended, but GOG could probably have negotiated a new deal if that were the case. The other reason could be linked to the future of the Fallout franchise as a whole.
This doesn’t necessarily mean a link to Fallout 4, as the games remained on sale during the launches of Fallout 3 and New Vegas. It could be that Bethesda have their own plans for the games, but that wouldn’t explain why the games are still available on Steam.
Maybe Bethesda didn’t like GOG giving the games away for free a couple of weeks back.