SmartMarkUP is completely customizable and scriptable as well. Changing styles, implementing new markups, creating extra buttons and submenus or adding new functionality is a matter of minutes. SmartMarkUP is distributed under GPL open source licenses, so SmartMarkUP is absolutely free and you can do anything you like with it!
Requirements: Safari 3.x, Firefox 2.x, Firefox 3.x, Google Chrome, IE7, Opera
License: GPL License