As stated in the title, if you don't have a jtag xbox 360 or aren't planning on getting one, this information is useless to you. But you can still create custom songs for Guitar Hero 2 if you have a system that can play burned games. Look here for more information:

I was looking around on the net and I found this guide on how to create custom songs for Rock Band 1 or 2, which would be a wonderful break from using Gh2 as a custom song platform with its outdated graphics.