Extract the zip to "My Documents\My Games\Unreal Tournament 3\UTGame\".
Usage:
When starting a game, the mutator will show up in the mutator list as normal. If you wish to configure it, select it in the list of enabled mutators then click on the "configure" button at the bottom of the screen.
* Gib Multiplier: The number of gibs will be increased by this factor. Setting very
high will slow down your computer. Setting ridiculously high may cause a crash.
* Gib Friction: This option is currently disabled.
* Gib Restitution: This option is currently disabled.
* Gib Speed: Controls how fast gibs fly.
* Gib Life: Gibs last this many seconds longer than normal.
* Extra Splatters: Enable this to force all weapons to cause blood splatters on hitting (usually only the bullet weapons do this).
The configuration menu limits the values you can set to reasonable quantities. If you want to experiment with more extreme settings, you can edit them in UTMutator_Gibalicious.ini
Note that you may not see all the extra gibs if you have low gore enabled, you have world detail set very low, or you are running below MinSmoothedFrameRate.
All options are client-side, so the settings you choose on your computer will be used for you if you connect to a multiplayer game running this mutator.