Not sure if its flame retardant.
I should say I assumed it was similar to the projection screen and not fabric. It may be. They do offer a few different options.

For less than $500 you would have a XD screen on a DIY screen frame. Its possible you could upgrade to the newer screen inside the $500. Seymour has 2 sites, if you go DIY you will want http://www.seymourav.com/screens.asp .