OfficeJS Text Editor app is a progressive web application developed with renderJS and jIO under the premises of privacy and availability, meaning users are free to choose their storage, can work offline and synchronize their work easily. Text editor application is developed, maintained and used by Nexedi, and its code can be found here.
The editor itself is based on CKEditor software. The source code of CKEditor can be found here.
OfficeJS Text Editor is Free Software, licensed under the terms of the GNU GPL v3 (or later). For details, please see Nexedi licensing.