When will FoldingText be available on iOS or Windows?

We don't know.

Right now our focus is on the OS X version. As that settles down we'll be looking to get FoldingText on other platforms. This is something that we've planned for from the start (that's why the vast majority of the code is in cross platform Javascript/DOM). But it's a big picture plan, we don't have a schedule, and we are not actively working on a port at this time. We expect to be working on the FoldingText codebase for many years to come. It makes a whole lot of sense to port to other platforms as soon as we can, and I think we will. But for the time being the focus is OS X.