As with most elements of HLP's policies, there is room for flexibility and interpretation in the way we approach the posting/use of copyrighted works inside and outside the context of FS mods. In this case, as with many others, the sin doth lie in the intent.
In my non-professional opinion, the use of copyrighted game music in another game mod, for profit or not, is probably not legally defensible as fair use. However, the copyright owners have not caused a fuss, and the material is used in a separate work, and is used exclusively in support of a FS mod, which is the exact kind of activity that HLP supports. So while the use of said music may technically violate the general anti-piracy stance, we turn a blind eye in cases such as this for the good of the modding community and FS as a whole. Of course, if the original owner were to complain and/or issue a take-down notice, things would quickly change.
Compare that scenario with the general posting of, for example, a torrent for an album. The torrent adds nothing to the FS community or modding scene, so we would come down hard on it.
I can see how some people would see this as a double standard, and maybe it is, but I think it's a double standard that gives the community the best balance possible, and prioritizes the things that are important to us.
Please note, however, that all that is my personal opinion and interpretation of our rules and precedents. This hasn't been discussed behind the scenes as far as I know, so don't take this as any kind of official HLP stance. It's simply how I approach the issue as a mod.