CKEditor - Real-time collaborative future-ready rich text editor
Dabble Writer - Writing software for novelists.
Summernote - Summernote is a JavaScript library that helps users create WYSIWYG editors online.
SHAXPIR - A modern cloud workspace for fiction writing & worldbuilding
Froala Editor - Froala Editor is a WYSIWYG HTML editor that enables rich text editing capabilities for the applications.
Manuskript - Open-source tool for writers.