I am a bit unsure about the license in CKeditor.
When I am making a Content Management System which I am “selling” to customers, how am I allowed to use the CKeditor in this System?
The payment method is about setting up the system – the System it self is “free”.
As long as you provide the source code of your work either directly or upon request, there is nothing stopping you from selling a product that includes software licensed under the GPL.