Forth was neat, but it was a bit of an evolutionary dead end. I'm not aware of any significant concepts from Forth which were adopted by other, later programming languages.
RPL (Reverse Polish Lisp, a high level language for HP calculators) possibly drew on it a bit, though the main antecedents are RPN and Lisp, and possibly Poplog (a Poplog guru was at HP at the time, but I don't know if he contributed).
The only thing PostScript and Forth have in common is RPN. Other than that, they are very different in philosophy - Forth is very bit banging, close to the metal, while PostScript is much more symbol oriented and high level.
That's true, PostScript is much higher-level and feels like a stack-based LISP. But, saying they just have RPN in common makes it seem like a small choice about the syntax - instead of a whole stack-oriented approach, which affects everything.
Well, yes, the stack oriented approach does matter. But even there, there are big differences with Forth having a user accessible return stack, which is implicit in PostScript, while PostScript has an explicit dictionary stack, which exists only in a very primitive form in Forth.
Did Forth inspire the stack-based VMs of python and java? I don't know about that part of CS history well, but a very large proportion of all code runs on stack based byte code interpreters.
