Are there programs that can 'translate' source code between any two languages?
TLDR; this is possible but not practical.


  (assuming the translator has access to the requisite libraries)?


This ends up being the tricky bit, and is part of why things like this don't end up being used in practice.


All compilers are translators. Translating from one language to another is definitely possible, and this is literally all a compiler is doing. The language that a compiler spits out as output is generally machine code or assembly, but this is just another language, and there are compilers (sometimes called transpilers or transcompilers) which translate between two languages. For example, there's a gamut of compile-to-Javascript languages like PureScript, Elm, ClojureScript, etc.
Translating between any two Turing Complete languages is always possible. Ignoring things like library calls and FFI and other nasty practical bits that get in the way, that is. If a language is Turing Complete, then you have:


A translation that converts a Turing Machine to code in this language
A translation from this language into a Turing Machine


So to translate from language A to language B, you convert the A code into a Turing Machine, then convert that machine into B code.

Of course, in practice, the practical bits get in the way, and this also requires you having the translations accessible to you. They exist for basically every language, but that doesn't mean someone has taken the time to write them out.
Doing this translation efficiently is hard. Different language prioritize different things. For example, if you translate from C to Python, you're probably going to have to end up simulating C's memory as a Python dictionary, so that you can do pointer arithmetic. There will be overhead associated with this, because you're now not accessing the bare metal memory instructions.

Different languages have difference performance priorities, so something that one language optimizes (or rather, an implementation of one language optimizes) might be impossible to do quickly in another language. Translating a functional language with proper tail calls will have slowdown if you translate it into a language without proper tail calls. 
Doing this translation doesn't make the code readable. It's easy to get a piece of code in language B that behaves the same as the code from language A. It's hard to make it look like code a human would have written in B, for a number of reasons. A and B might have different abstraction tools, and the computer has no idea what makes code readable. This will be particularly true if you end up using the Turing Machine translation I described earlier. 

This raises the question: what's the point of such a translation? If all you get at the end us a block of slow, unreadable code, why not just compile it to machine code and use some kind of FFI or inter-process communication to link the pieces together?

There are some exceptions to this. Sometimes you need things in a certain language (like JavaScript). Sometimes language are similar, and a sensible translation is easy. Sometimes a language is not meant to be run, but to have its code extracted into another language (such as Coq).

But in general, it's not a very practical thing.