Microsoft purchased Bungie in 2000, and in 2007 spun the company off as an independent entity, Bungie LLC. In the interim, Bungie Studios developed and Microsoft published Halo, Halo 2, Halo 3, Halo 3: ODST, and Halo: Reach. The deal that made Bungie independent gave ownership of the Halo franchise to Microsoft, who have assigned it to new in-house developers, 343 Industries. Halo 4 was 343i's first Halo title. 
Bungie was allowed to retain ownership of the Marathon franchise.
Former shareholders in Bungie, Take-Two Interactive, received ownership of Bungie's Myth franchise as part of their compensation for their stake in Bungie when Microsoft purchased the studio.