If you are looking for Dreamweaver like functionality in your own
editing tool, then check out the Webdesigner component at
invivosoft.com.

It has the following features -

1. Source code preservation.
2. Rendering/translation of custom content
(custom tags, include pages etc.)
3. JSP rendering engine.
4. Object model for programmatic access/manipulation of document.

and more ...

visit http://www.invivosoft.com/products.html