What can replace vegetable butter?
Look for the kosher symbol on different types of butter.  You will need to find a substitute with the word "Parve" on it.  Parve means no dairy products.  From there just check the labels to make sure it is gluten free.  Other things that I have used to replace butter have been olive oil or applesauce (works great in brownies).  

Here is a chart if you would like to substitute olive oil for the butter.  http://www.amazingoliveoil.com/substitute-olive-oil-for-butter.html