The Hopper Engine is based on the Tier666 mod (a mod aimed at making the bots more like human players). It's goal is to make the bots act more like bunny hopping players. It's an engine change so it can potentially be used with any existing Quake III Arena mod. They have just released version 3.0. Here's the list of features:
- supporting almost all the maps and mods ever released on the fly (mods that have modifed movement physics or bot AI are unlikely to mix well)
- movement AI quite different from original Quake III Arena
- map roaming AI quite different from original Quake III Arena
- wider range of render setting
- sampling human player jumps from demo file as a helper waypoint for bots
Check out their full news post and download the new engine to give it a test run.
Here's a video of it in action with Q3A's CTF mode: