I think sometimes people get a bit hung up here.

The tunes to Child that Bronson discovered (generally speaking) are available since he found them.... so can anyone else.

But there is no need to restrict the tune to say "Riddles Wisely Expounded" to that ballad. Each tune can be adapted, adopted, borrowed and so on....just see Bronson as a starting point would be my advice.

There is a good biography here
though it doesn't emphasise (enough) why he disliked the earlier version he did in the 1850's. He later realised it was not the precise work he wanted so he devoted himself to tracking down original sources.

Let me get the original out and I'll come back later....

Dave