In the FAQ section, they mention a "Cloud IDE" named Brightly, which frankly seems more interesting than the language itself:

"How does this affect our cloud IDE (Brightly)? Brightly will enable building any web application in V1 using today’s Javascript plus the additions in Harmony. As soon as it is ready, Brightly will support Dash as well. We expect that the more prescriptive development aspects of Brightly that will come on line in the future will be more Dash focused."