GOG is giving away Saints Row 2 to celebrate the DRM-free release of Saints Row IV: Game of The Century Edition and Saints Row: Gat Out of Hell. But you should hurry, because they aren't giving it away for eternity. It'll be available for free until April 22 at 11:00 AM GMT/ 3:00 AM PT/ 6:00 AM ET.
Btw, both Saints Row IV: Game of The Century Edition and Saints Row: Gat Out of Hell are currently discounted by 75%. Making them sell for $4.99 and $3.74 respectively.