The 360 version will be available for anyone who downloads it today forever, while the Xbox One version is only available to play today as a free trial. Note that the trial version still acts as if it’s the full game and achievements will unlock.
Achievement hunters should take note of this as the game only takes around 2-4 hours to get 100% of the achievements. This could be a free 2000 gamer score if you’re fast and complete the Xbox One version today! Just prepare to get angry at the “Flappy Goat” mini-game.