Question Interactive Demos/Stories

Planning to launch Collab in the next 30 days on PH. I've launched on PH in various roles, but I just noticed a "new" ability to post a link to an interactive story. Is ScreenSpace the only supported URL for this? PH has an ad for ScreenSpace that makes it look like it should be free, but after signing up for an account we'd only get a 30-day trial of ScreenSpace. Since our launch is at the very tail-end of that window, our audience wouldn't be able to use it. Any suggestions/thoughts?