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On October 12, Warhammer 40,000: Space Wolf and all of its DLC will be removed from the Steam store.
(store.steampowered.com)
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Very likely a license problem, with the Games Workshop not renewing the W40K license for HeroCraft (the game developers). I hope not too many recent games actually get unlisted from Steam because of music licensing issues, when a simple solution would be to remove said music in a patch.