Starbar may be a local nickname, It is a t-slot style aluminum extrusion bar that has special slot nuts and brackets. It is very versatile and many team use it for their frames because it is strong and easy to fabricate with. IMO it is crazy heavy though. Weight/ft is significantly higher than most other materials, but it is strong and if it saves you 1 week in the build season the weight penalty can be worth it.
Here is a link showing the cross section
http://www.aline1.com/products/?categoryID=16
When you see the cross section you get the nickname.
I know 494 used this through 2006. When I asked them why they sighted 2 weeks of practice with the robot. Hard to argue with that. We will likely stick to a sheet metal chassis, or a welded stickframe.