Currently you can only create a project by cloning an AppBuilder project. The link you provided is not a valid AppBuilder project. However there is a workaround to achieve what you want.
1. You need to download your repository as a zip.
2. Create a new project from template in AppBuilder
3. On the top left of the screen choose Add -> From Archive (or right click on the file tree and choose Add -> From Archive)
4. Chose your project zip file (the one that you just downloaded)
5. Your github project will be included in AppBuilder
If you need any further assistance please don't hesitate to contact us.