Xbox Live Marketplace as part of the Games on Demand program, priced at $39.99. That's despite Silicon Knights being ordered by the US court to recall and destroy all unsold copies of its products using Unreal Engine 3, of which X-Men: Destiny is one. The company was also ordered to cease producing and distributing games using Epic's technology.
So what exactly's going on here? Well, the ruling in the Silicon Knights vs. Epic Games case dictates Silicon Knights notifies the US court by December 21 of its compliance with the injunctions ordered. This is presumably to give Silicon Knights adequate time to carry out the required actions; recalling and destroying every unsold copy of X-Men: Destiny and Too Human.
So the game newly appearing on XBLM might not contravene the injunctions, at least for now. It should also be noted that Too Human is also currently available on XBLM, while GameStop, Target, and Best Buy all have new copies of X-Men: Destiny listed as available.