Osage Orange, in my experience is pretty easy to grow from seed. Just
collect those big green fruits, stick 'em off in a corner somewhere, maybe
buried under some leaves, and allow them to become fully bletted. You can
then pick the seeds out. They have a slight dormancy requirement,
requiring 30 days or so at 40 degrees F, or by soaking dried seeds for a
couple of days, according to Dirr.
I tried rooting pre-callused hardwood cutting a year or so back, but
failed; but I had just stuck them in the ground, not in a rooting bed with
bottom heat. Supposedly, softwood cuttings, taken in July, root quite
readily when treated with IAA.
An intergeneric hybrid between Maclura and Cudrania has been described(X
Macludrania), but I know nothing about its form or fruiting habits.