It's called disruption if force powers are used; normal instagib only has force jump enabled. Disruption servers died out in JK2 a few years ago and were replaced with normal instagib.
The .[mVp]. InstaGib (22.214.171.124:4004) CTF server is still up atm, check it out if you want to get a feel for the game.
If you want to run instagib on your server you'll need CJK-Mod: http://files.filefront.com/CJK+Mod+0.../fileinfo.html