Can I use Gust Launch if I am NOT a US citizen but I am based in the United States?

Yes, if the co-founder who will be CEO has a US Social Security Number or ITIN. It is very important to note, however, that you CANNOT then use your own company to sponsor you for an H1-B work visa in the US. So while you may end up owning a US company, you paradoxically may not be able to work for it.