A: OK, here's the complete genealogy of Halo.

Bungie Studios, a part of Microsoft's entertainment division and formerly the Bungie Software Products Corporation of Chicago, Illinois, is the original developer of Halo, published by Microsoft for the Xbox console. Gearbox Software, of Half-Life add-on fame, was contracted by Microsoft to port Halo from the Xbox to the PC (which is to say, Windows and DirectX9). Gearbox then supplies their Windows code to Westlake Interactive, which is porting Halo to the Mac, which will be published by Destineer Studios (MacSoft).