The oral tradition is less important than the early collectors supposed, and the print tradition more influential than most of them realised or liked to acknowledge. The majority of songs considered "traditional folk songs" at the beginning of the 20th century had appeared on 19th century broadsides. Some were older than that; many were not.

It's an extremely interesting subject, and (though a lot more work has been done on it than is often realised) there is still plenty of scope for exploration. I don't know that it affects materially the working definitions that we'd use today when considering whether or not a song has "entered tradition" or is simply being transmitted aurally (not necessarily the same thing). Copyright issues are, if not completely irrelevant, misleading at best: not useful criteria anyway.