The classic back catalogue of Fallout titles previously available on digital retailer GOG's website has been removed due to a rights issue originating from Bethesda's acquisition of the license.
A $2 million settlement was reached in January 2012 that gave Bethesda control of the franchise and all of its assets, with the transfer of all Fallout IPs due by December 2013. Now it appears that the ruling has finally kicked in, barring GOG.com from selling any titles in the series from their online shop.
Oddly enough the series is still available on Steam, suggesting that there may have been issues between GOG and Bethesda regarding the transfer. It remains to be seen whether the Fallout series will eventually make its way back into GOG's non-DRM distribution service.
Meanwhile, those who purchased the game during the recent Winter sale will be happy to know that they can still download the game. GOG were quick to point out that.