GOG 'reclaim your games' revives S.T.A.L.K.E.R. Gamespy keys, also activating on Steam

Related Games:
S.T.A.L.K.E.R.: Clear Sky, S.T.A.L.K.E.R.: Shadow of Chernobyl, S.T.A.L.K.E.R.: Call of Pripyat, Mount & Blade: Warband, Mount & Blade: With Fire and Sword
Source:
GOG.com