ZeroGox is a hosted version of goxtool, an open source MtGox trading bot written in Python and using a rebalacing strategy. The aim is to make Bitcoin trading more accessible by lowering the adoption barrier.
The open source project is here: https://github.com/caktux/goxtool.
ZeroGox is simply a hosted version of this. You can try it for yourself and run it freely on your own computer, contribute or not, and that's how it will stay. This hosted version is simply for convenience and an attempt to make trading more accessible. Settings are exposed in the web interface of your account and an address will be provided for you to SSH to your trading bot. You will need to upload a public key to authorize yourself and will then be able to add your MtGox API token and secret when and only if you want to, just like if you were using goxtool locally.