Someone got this working with ruby (rails). There's a gem/plugin out there that gets the file uploading/system working (I believe it relies somewhat on paperclip,etc). Sorry for being so vague, but I'm sure Google will turn up something.
There really is a huge hole in the market for a Rails-integrated WYSIWYG editor. There are tons of PHP ones. What I'm seeing is a lot of people are forced to run PHP on their server just for the editor and load it through AJAX.
Hopefully soon there'll be more ports of editors to Ruby.