Free standing gas fireplaces, gas fireplace inserts and in this segment from my TV show, a cross breed between the two put a very inefficient fireplace back into operation. Yes you need a chimney liner when you do something like this - that is the duct sticking out of the fireplace in the photo. In fact you should always have a chimney professional check out your chimney any time you change its use -- especially when you change from one fuel to another.
It is also important to study the relationship between the exhaust fans in your house and this chimney. Can the fans cause problems? Check out "Spillage Susceptible" in the keywords search for more information.
The installation was by an Enbridge Gas installer in Toronto.