There is a “notes on the new name” section on the linked article:
“For years we have been fighting with a relatively important issue with FCKeditor. While its quality has been strongly accepted, its name brought us troubles, mainly inside English speaking countries. The fact is that the initials of Frederico Caldeira Knabben have an unfortunate match with the most used English bad word.”
Interestingly, I swear FCK was the creator's initials - I wonder if the app's name change is a reflection of a name change on his behalf? ;)