I'm currently trying to integrate WIRIS formula editor into CKEditor using the Wysiwyg API.
I've successfully created a module (based on this) that does just that, although not without some problems along the way:
First of all, I had to copy the ckeditor_wiris plugin into /sites/all/libraries/ckeditor/plugins/ and set write permissions on the cache and formulas folders (as indicated on the WIRIS website).
When I then activated the WIRIS formula editor in the Wysiwyg profile, ckeditor wasn't loading in the Add content form (completely blank). Looking at the JS error console, I saw that CKEDITOR.config[_wrs_toolbarName] was undefined and prevented the plugin from loading. I simply commented out the whole for(...) loop (lines 52-62) that was used to prevent a bug with multiple ckeditors on the same page. It worked! I can now use the formula editor and CAS !!