CKEditor is distributed under both Open Source (GPL, LGPL or MPL) and commercial licenses.
More information about CKEditor licensing options is available here: http://ckeditor.com/license. The full text of the CKSource Closed Distribution License Agreement is available here: http://cksource.com/cdl.
If you are not sure which licensing model is appropriate for your CKEditor usage, please use our contact form to describe your business model and needs.