At this time in Oklahoma a wild hog can be sold to ANYBODY as long as it isn't transported alive. If the hog is transported alive it MUST be transported by somebody with the proper permit. Processing plants are supposed to only process live animals, thats why most butchers who process deer shut down butchering of beef during deer seasons.
Myself, I've never come across a processor that will do a feral hog. Probably varies, but just because someone is a processor, don't pull up with a truckload of dead pigs and expect them to start butchering without checking first.
I thought the transport laws stated that you could transport under 30 miles without a license, but just read the statutes and there is no mention of that. Fired of an email to the Dept of Ag to get clarification. Makes sense that you should be able to transport very short distances for your average trapper taking them to sale. But of course then everyone would be "just going down the road, Officer".