GitX is an open source project. This means that you can help developing or even take the code and develop you own version. GitX is released under a GPL v2 license.
If you want to contribute to GitX, you can just clone the repository and start working! The GitX repository can be cloned by using:
git clone git://github.com/pieter/gitx.git
The preferred way of contributing is by sending patches to the Mailinglist.
If you're not sure what to do, you can take a look at the TODO list on Github. If you want to work on the HTML side of GitX (such as the detailed view), you should take a look at the Working on HTML page.
If you find or want to fix bugs, you should take a look at our Bug Tracker. If you can't reach Lighthouse or don't want to register for an account, you can also send the bugs to mailing list.