The root directory in the git repository doesn’t contain build scripts (build.gradle, settings.gradle), only the environment and samples directories do. You should only import those projects.
I’ve tried to do just that and there seems to be a bigger problem. The projects require Gradle 2.2, which is really old. So old, that not even Buildship supports that. You should request (or try) updating the project to use at least Gradle 2.9 to be able to load the projects into the workspace.