ks_osage_orange
ArboristSite Operative
Could these be a species of Aralia? Maybe Aralia spinosa? It goes by many common names, such as devil's walking stick, hercules' club, prickly ash, etc.
Aralia spinosa or Devil's walking stick was one that I was looking at also, but the trees in the picture all seem quite large, but probably not outside the range of the species so it may be possible, and the way he describes them growing in clusters and having lightweight wood makes it a possibility??? We may not find a definitive ansswer on this one.