Halo 4 was the first game where Grifball was included as its own stand-alone gametype. 343 Industries consulted with long-time Grifballers while developing the game to help make the Grifball experience as awesome as possible. 343 also asked GrifballHub to showcase the gametype publicly for the first time at PAX 2012.
The Halo 4 Grifball playlist went live in January 2013, two months after the game launched. The playlist is maintained by GrifballHub and 343 Industries, and every map and gametype that is submitted to 343 Industries for inclusion in the playlist comes from the GrifballHub community.
If you would like to submit your Grifball map for possible inclusion in matchmaking, or you need help making your Grifball court, please see our Grifball map forum. Forge experts runNOKYARDrun and Nuclear Taco 42 will be happy to help!
Though grifball first made an appearance in Halo Reach matchmaking in January, it wasn't until February 8th, 2011 that it officially became a permanent playlist.
You can see screenshots from the maps currently in Grifball matchmaking. If you'd like to download them to use for custom games, they can be found spread out between two file sets - Grifball Matchmaking 1 or Grifball Matchmaking 2.