Available to claim till 3rd September.
Syndicate Plus™: https://www.gog.com/game/syndicate
Syndicate Wars™: https://www.gog.com/game/syndicate_wars
Ultima™ Underworld 1+2: https://www.gog.com/game/ultima_underworld_1_2
Syndicate is also available for free on Origin Store (until 3rd September, possibly Ultima Underworld 1 & 2 will be available here later as stated in the bottom text): https://www.origin.com/irl/en-us/store/deals/augustclassics