Legal insanity. When a guy can't use his own last name, nor display a photograph of his own father due to legal restrictions, that's just plain nuts. And to make it even more surreal, the entity enforcing the prohibitions has the disingenuous name of "Zappa Family Trust". With mom 'n dad gone, that leaves only the two kids to comprise the Zappa family, which apparently the family trust does not represent. Insanity.
And you're right; Frank would not approve.