There comes a time when it's necessary to create a prototype for our web development projects. When this time comes, usually we have to depend on designers to create a PSD file, then work with him(or her) to generate a valid HTML and finally use the generated HTML in our Ruby,Python or PHP template system.
Twitter's Bootstrap, enables designers and developers to work easily. By providing a common framework to place thing in a web template by stablishing some standard CSS styles.
Twitter's Bootstrap and these templates are released under the Apapche License Version 2.0
http://www.apache.org/licenses/LICENSE-2.0
You can check these templates at: Heroku's Bootstrap 101 Page