i've definetly read that film uses gelatin, like when you see a movie they use gelatin on that film too. kind of sucks. actually, no it really sucks. i never thought about glossy paper though, that's a really good question. ???
and yes they have tried using many other things to make film of, none of them worked well enough to go into production. there's some interviews with glen e. friedman (famous band/skateboarder photographer) who's a vegan where he addresses this and mentions how he's actually worked with kodak to develop a non-gelatine based film.
he suggests people get into digital photography, which with the new digital slr's is a viable alternative.