It’s debatable. Some big projects like bootstrap and lodash publish build artifacts to GitHub. Some other projects do this, but not in the master branch. I believe the reason for this is to enable installing with Bower.
That said, I’ve removed the lib directory, since I’m actually in favor of npm for all the things.
@pascal one challenge I see with this approach is the difficulty to know the generated API. Is there any change you have thought of an easy way to see this other than building another webpage or calling help on console?