Except that some jurisdictions in the world don't have the concept of public domain, so, in those places, this code is legally in a very weird place. It's much better (IMO) to assert copyright, and then release under the most permissive license possible.
It just sounded as if being public domain somehow makes project more ambitious (that is, means to be more difficult to complete than if it wasn't public domain), so I probably just misunderstood.