Извините, но я не смог найти ничего (даже на официальных страницах), информирующего меня о различиях между двумя версиями.
Даже вопрос на их официальном форуме оставался без ответа в течение многих месяцев -
Страница лицензии немного говорит о "внутренних" различиях
CKEditor Commercial License - CKSource Closed Distribution License - CDL
...
This license offers a very flexible way to integrate CKEditor in your commercial
application. These are the main advantages it offers over an Open Source license:
* Modifications and enhancements doesn't need to be released under an Open Source
license;
* There is no need to distribute any Open Source license terms alongside with your
product and no reference to it have to be done;
* No references to CKEditor have to be done in any file distributed with your
product;
* The source code of CKEditor doesn’t have to be distributed alongside with your
product;
* You can remove any file from CKEditor when integrating it with your product.