Maqetta is an open-source project providing WYSIWYG visual authoring of HTML5 interface. The application itself is based on HTML and runs in the browser without requiring additional plugins or downloads.
Maqetta allows UXD (User Experience Designers) to perform drag and drop assembly of live UI mockups. In fact, one of Maqetta’s key design goals is to create developer-ready UI mockups that promote efficient hand-off from designers to developers.
Mqetta is available under comercial open source licese so you can download the source code and install it on your own server, customize it to fit your needs or you can contribute to make the source code better.