https://github.com/LLK/scratch-gui/wiki/Getting-Started#example-scratch-gui-vm-and-blocks-linked
mkdir scratch && cd scratch
git clone https://github.com/aubrune/scratch-gui # if making changes fork the project and check out your copy
git clone https://github.com/aubrune/scratch-vm # if making changes fork the project and check out your copy
git clone https://github.com/aubrune/scratch-blocks # if making changes fork the project and check out your copy
cd scratch-vm
npm install
sudo npm link
npm run watch
cd ../scratch-blocks
# Edit package.json to force python2 in entry prepublish
npm install
sudo npm link
cd ../scratch-gui
npm install
npm link scratch-vm scratch-blocks
npm start
http://localhost:8601