I would like a form where customers can drag and drop basic shapes to graph paper, alter their size and color and place text within the shape.
This is saved as xml. Later, admin can login and edit this xml and save their edit as a revision of the original diagram.
Must be simple and lightweight, no frills are needed.
Should support most popular browsers with graceful fallback to "Sorry, your browser (browser name) is not supported."
Feel free to use any or all free or open source code that does not place restrictions on commercial use.