This is always a sticky question, and I don't think there are clear-cut answers. If we put too much effort into protecting copyright (and whatever rights by transcribers of traditional songs), we also serve to restrict access to the song somewhat.
If I find a MIDI or lyrics for a traditional song on another Website, is it wrong for me to post it at Mudcat?
I fully support the rights of living songwriters - but if we're too careful about protecting rights, aren't we likely to be helping songs disappear?