Is the contract of interest between the author of the GPL code and the buyer of the Vizio TV, so that the buyer would have a claim of tortious interference against Vizio?
It's not tortious interference but rather "3rd party / intended beneficiary" coming into play here. The idea is that the contract between the author and Vizio was for the benefit of a 3rd party (the end user) and so that party has the right to sue.
For another example, think of someone who is hired to handle disbursing an estate by someone who is dying. Their kids/heirs can sue the executor for contractual issues if the executor does anything shady because even though they weren't party to the contract because they stood to explicitly benefit.
