First of all I'd like to address some issues that might get this question closed.
- This question does not belong here! I didn't feel like posting it here either, but where should I post it then? It certainly does not belong on game-dev.
- This has already been answered here: What are the licensing terms for Portal 2's soundtrack? No it hasn't, that's for video games. This is merely a custom map for an already existing video games.
- This is a legal question. We are not lawyers AFAIK there's no stackexchange on legal affairs.
Valve states here that they're fine with players using their assets (which also includes music) for creating videos, as long as they're not distributed separately. I'd like to use their music for a custom Minecraft map, which, to be honest, I don't think can be categorized as a video.
Also, what is their definition of "separately"? Do they mean that I can't distribute the raw file alone or that I can't distribute the file without any other sound overlapping?