From what I understand juglone isn't present in the wood. Besides that, only certain plants are susceptible to juglone.

The Juglone is present in all parts of Walnut but in varying amounts that may not have much affect on plants growing under a mulch of wood from those trees. Most of the Juglone is concentrated in the roots to keep plants that could compete with the Walnut for nutrients from growing nearby.
I find the nuts from my Walnuts all over the place, destributed by the squirrels so where the nuts are may not have any other part to the tree.

I recall seeing a two paper article about Juglone and Walnut trees a while ago. Search 'juglone' on Google.

Different parts of the walnut tree had varying amounts of the compound juglone. Leaves were the easiest part to compost.

"Black Walnut Toxicity" W. Virginia University
Don't think this was the short article I referred to above, but it may answer your question.

There are also threads in this forum about juglone with some good links in them. It would take a little searching. But I think kimmsr has it anyway.