With no strings attatched.
GOG.com are currently offering 1 comic, 1 DLC and 13 games for "free!" Here's a list of those DRM-free titles:
Free comic:
- Hotline Miami 2: Wrong Number - Digital Comics
Free DLC:
- The Witcher 3: Wild Hunt - Free DLC Program*
Free games:
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Akalabeth: World of Doom
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Beneath a Steel Sky
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Dragonsphere
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Flight of the Amazon Queen
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Lure of the Temptress
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Starguner
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Teenagent
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Treasure Adventure Game
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Tyrian 2000
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Ultima 4: Quest of the Avatar
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Ultima Worlds of Adventure 2: Martian
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Warsow
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Worlds of Ultima: The Savage Empire
*Requires the base The Witcher 3: Wild Hunt game.
Image credit: GOG.com