This is the Mathslate editor adapted as a standard plugin for TinyMCE4. In order to add Mathslate into a local installation of TinyMCE4, copy plugins/mathslate to tinymce/js/tinymce/plugins/mathslate. Otherwise you may run TinyMCE4 from CDN by copying this directory to a web server.
Mathslate is copyright 2014 by Daniel Thies email@example.com and licensed under GPL version 3. Mathslate was originally developed for use in the Moodle platform using MathJax for rendering mathematics. These files are a crude adaptation from the Moodle TinyMCE plugin.
Try the Mathslate Plugin in theTinyMCE4 Editor here. Use the button on the toolbar or
Insert Math in the menu to create a TeX expression.