You may have heard of MIT Scratch <http://scratch.mit.edu/>, a visual programming language oriented to teaching children programming. Initially I was put off by the non-Free licence (you couldn’t redistribute modified code), but that seems to have gone now, and the source is available <https://github.com/LLK/Scratch_1.4> under completely Free licences, the core being GPLv2, plugins under an MIT licence, and support materials/samples under CC-BY-SA. Google has its own alternative along the same lines, but Web-based, called Blockly <https://code.google.com/p/blockly/>. And Barack Obama has successfully used it to become the first US president to write a computer program <http://www.engadget.com/2014/12/08/barack-obama-just-became-the-first-us-president-to-write-a-compu/>.