I looked in my basement and I have all the gas lines run with this product.
http://www.omegaflex.com/trac/index.asp
The lines run about 20', 10', 10', and almost 60' (to a gas fire place). My Father -In-Law is a pipefitter at an oil refinery and told me the approval is on a county by county basis. Check with your local Building Inspector.
I am not sure whether you can purchase the line as a home owner. My F-I-L also mentioned you might have to be a card carrying member of a gas affiliated organization to purchase it, he will be doing my gas work as I finish the basement, so I am not worried about availability. But you might be able to get it.