Liberty is the first Halo 4, Halo: Reach, Halo: Combat Evolved Anniversary, Halo 3, and Halo 3: ODST campaign editor that is 100% free and doesn't require registration. It also supports more features than all of the current editors around. 100% of it was made from our own research and we had no help at all from anyone who already had information on campaign saves. It is licensed under the version 2 of the GNU General Public License (GPL).

Liberty was developed by 3 people:

AMD: Backend Code/Research
Xerax: GUI/Backend Code/Research
Thunder Waffle: Research

anniversary/halo 3/odst/halo 4;

Biped Manipulation: Edit your player's position and make yourself invincible.
Weapon Manipulation: Modify the ammo for each of your weapons, and max out the ammo of every weapon loaded in your save.
Grenade Manipulation: Give yourself more grenades.
reach;

Biped Manipulation: Play as another character, clip through walls, edit your player's position, and make yourself invincible.
Weapon Manipulation: Modify the ammo of each of your weapons, switch them out with other weapons on the map, or even give yourself four weapons total. You can also max out the ammo of every weapon loaded in your save.
Grenade Manipulation: Give yourself more grenades.
Object Manipulation: Want an AA gun on your warthog? Want your Ghost to shoot Scorpion shells? Liberty's object editor is very powerful. Move, delete, resize, or swap any object in the save. Make enemies weaker. Attach objects to each other. The sky is the limit.
Fine Tweaks: Edit checkpoint HUD text or weaken every enemy in the map.