Eduardo Cavazos has been working on an X11 bindings library for Factor, and a window manager named Factory. Here is a screenshot. Cool stuff!
Doug Coleman is working on Win32 bindings, and I will later start work on Carbon (Mac OS X) bindings. These three libraries will be used to build platform-specific backends for Factor's UI, replacing the SDL library we use now.
My hat goes off to all the contributors; there's 6 people (not including me) hacking Factor now, which is ideal this stage of the project.