You can signup and use the production Greenhouse instance at http://greenhouse.springsource.org. However, you'll want to checkout the source code to really study it, adapt aspects of it to your own needs, and contribute to its development. Follow the steps below to get an embedded Greenhouse instance up and running locally:
1. Clone the Greenhouse project repository at http://github.com/SpringSource/greenhouse
2. Import the project into the SpringSource Tool Suite (STS) (version 2.5.0.RELEASE or > of STS is recommended)
3. To deploy the app, drag the 'greenhouse' project over to the "SpringSource tc Server Developer Edition" instance in the Servers view.
4. Start the server and access http://localhost:8080/greenhouse in your web browser. You'll know if it worked if you see the home page.