https://www.law.cornell.edu/uscode/text/18/2332g states that just having a system "intended to launch or guide a rocked or missile described in... [description of MANPAD type rocket]" carries life imprisonment. He calls it a manpad and then shows a system intended to launch it.
There is no consideration in the law whether he actually plans to use it or ever meant any violence, nor any consideration of whether it violates ITAR.
As someone who has a lot of interest in weapons law, this is probably about the only kind of weapon that can't be even legally contemplated in the USA, worst case for almost anything else you can get an NFA stamp. The USA is absolutely paranoid about yielding their air power so they come down like a ton of bricks against anyone that might want to defend against that.
The theme is guidance systems. Especially guidance computers. That's the big big big no-no. I'm surprised this still hasn't been taken down and house flashbanged and all.
the links says explosives + guidance system, but guidance system still allowed in hobby project as long aim toward sun (eg. sun is the target, same for stabilization), I think having horizontal stabilization hitting an target would be equal to breaking law.
So design a system for launching test vehicles?