This is not a demo. You can get this on the market place but for those who don't have live here you go. I have not tried this yet so I don't know how it is, I'ii try it as soon as I can and post a comment on how it is but if someone else does first please let everyone know if its any good. The description below is by M$. Enjoy.
"Create, share, and download the most outlandish characters you've ever seen, then upload them for play in Saints Row: The Third. Inside every Sinner is a Saint."