I Love Lionhead. They don't even make it a big deal or anything, just quietly make it free.
And from E3:
The company will also bring two games per month, free of charge, to Xbox Live Gold members. The first two games are Assassin's Creed 2 and Halo 3.
Fable 2 was free when Fable 3 was coming out and I know they're making an HD version of Fable 1, so this is probably for that because it'll be shown at E3.