codeCanvas is a free, open source, visual web based editor that allows you to rapidly create layouts using predefined blocks of HTML, Javascript and CSS.
It writes the code for you.
The open source "codeCanvas Desktop" project is available on Github and the core can be downloaded here.
You can help out by making a donation, tweeting the project or forking the Github project. Get involved and help to make it better for everyone.
If you like codeCanvas, please donate to help insure the future development of the open source offering.
It costs money to keep codeCanvas open source and free. The advertisements help keep the lights on :-)
Here is the complete client side code for the codeCanvas editor. It is a streamlined version of the same code used in the codeCanvas Desktop project on Github.
Download the codeCanvas core - The complete editor and sample bootstrap tools
Here are a couple examples of what the open sourced code can do at the moment. All the canvas functionility is there but the integration with App.js needs work.