No idea on that point, but the subject came up among the moderators recently. No question that a license is required if you intend to make any significant income from doing it. Search past posts and you'll find folks have priced all this stuff out before.
If you're just selling a box or two along with a gun or in some other casual sale that isn't a part of your livlihood, then there isn't likely any legal issue with the sale itself. But I've heard people talk and seen posts about handloads they got with a gun proving to be surprisingly hot. Since the handloads aren't pressure tested in a commercial pressure barrel, and aren't subjected to other manufacturing quality controls, you take a much bigger chance shooting someone else's handloads in your own gun rather than the gun the load was developed in. Personally, I won't do it at any price. All handloads I've been given in the past, usually by someone who didn't have the gun anymore, I've pulled down to the components and fertilized the lawn with the powder, since I can't know how careful the original loader was about keeping track of it, nor what conditions it was stored in.