Extremetech says: "ThinkFree uses both AJAX and Java. The company admits that AJAX is more portable in that it doesn't require a plug-in, but they contend that Java is needed to provide true Microsoft Office compatibility and functionality. Solutions like ajaxWrite can mimic an installed word processor interface with some success, but ThinkFree's take is that they don't want to limit users to one browser, as ajaxWrite does. And ThinkFree goes a lot farther than ajaxWrite in mimicking Microsoft Office functionality. Note that the office suite doesn't include a database app, so it's not really a complete replacement for Microsoft Office."
TinyMCE is also used by Geneone, WordPress and Flock.