Hey, we are building an open source web tool for design and prototyping and looking for the contributes (developers, designers, content publishers...).
The goal is to build an open platform for designers and developers.
We already have rich design capabilities and you can also write a code for the prototypes in the embedded editor.
You can see current state here http://carbonium.io/app
The source code is here https://github.com/CarbonDesigns/carbon-ui
The project is written on typescript, es6, canvas, c# on the backend.