No real source information is given, so my initial impression is that the site has been put up by somebody who has no respect for the people from whom the tunes came or for those who originally published them. The Lewes Tunebooks are not 'public domain' (though they contain material that is, in other forms, public domain) and they have had trouble in the past with unscrupulous people pirating them lock-stock-and-barrel without permission.

At present the site is in what it describes as 'beta' mode, so perhaps proper information will be added by the time it officially goes live. Meanwhile, I'd treat it with caution until we know whether or not Lewes has consented to the reproduction of the material they have published without any of the contextual detail.