If you want to work on the default theme or need to work on the libraries, here's the steps:
$ git clone git://github.com/yui/yuidoc.git
$ cd yuidoc
$ npm link
This will link yuidoc into the global folder. This basically installs it globally as a
link to this source directory.
Now all changes you make to the current source tree are available in the global yuidoc
executable. No need to reinstall the app to test your changes.
You are also able to run unit tests by executing npm test.
$ npm test
For performance, the Handlebars templates are cached from the first request. So you will have to terminate the server and relaunch it before you can see your changes.
Assets should not be cached, so they should still serve new files on each request. This way you can modify the JavaScript and CSS files on the fly.
Pull Requests are very welcome, but should be within the scope of the project, and follow the repository's code conventions. Before submitting a Pull Request, it's always good to file an issue, so we can discuss the details of the Pull Request.
At Yahoo, we have a single Yahoo Open Source Contributor License Agreement that we ask contributors to electronically sign before merging in their Pull Requests.