There is currently a open development effort going on on fckeditor.net . Basically it seems that they want to rework a lot of their code and it seems that the new FCKeditor will be plugins based. I thought maybe it would make more sense if you guys would head over to the FCKeditor team and help them creating that shiny new core of their editor, maybe contributing some of your code to make it XHTML compliant. Then you could take that core, add some WYSIWYM plugins and a special theme and release that as the new WYMeditor.
This way you could profit from FCK's 5 year coding investment and stability, they would actually maintain the core in the future and you could concentrate on the WYM stuff. And maybe you could create a plugin that replaces their dialog system with jQuery UI's dialogs and maybe, you could release WYMeditor again as a jQuery plugin with integration to other jquery plugins. That would make the jQuery users like me very happy
(I would do it myself but I'm a complete javascript newbie...)