The federal government doesn’t give a rip if he could construct it over there.
You still need a license and you need to declare your export.
You need to declare WHAT you're exporting. You don't need to declare what the customer is ultimately going to use it for. One supplier is exporting steel cylinders of particular dimension and thickness. Another supplier is exporting nickel powder of particular degree of fineness. Etc.
I find it interesting that the prime detractors are currently shifting from "it's a fraud and a con and can't possibly work" to "it's a dangerous nuclear device and should be banned until he proves it safe" without at any point pausing at "well, it might actually be doing something in the area of cold fusion".