Secondly I think each of those should have a "Ported" section (unless there are serious issues with copyright and such, but if it works for models, skins and icons I don't see why it can't for sounds!).
This would probably work just fine for exported sound files like dialogue lines or sound effects taken from the HOTS Casc file system for example, but it also opens up for people to upload and share music files, which does indeed come with some issues related to copyright.
Having one or two copyrighted music files on Hive is probably not a problem. If the ones who owns the licensing rights to the track files a DMCA takedown not much will happen, other than Ralle having to remove the track from the website within a given time. That is no problem at all.
However, when this becomes a frequent thing, where a website repeatedly receives DMCA takedown requests there will be some penalties on the domain level. Not only that, but the web host may not condone such behavior, and may get you in trouble with them. I'm not sure, but it may also hurt the SEO, and lead to possible de-indexing from various search engines.
We also face the same possibility happening with the ported assets that are currently uploaded, but from what I have heard Blizzard doesn't care about their ported models being spread around, as long as they're not being monetized. That's also an issue with uploading music clips. Every time a music clip is listened to outside of its intended platform the original owner loses potential revenue, which makes it a bit different from using the ported models (which aren't monetized by Blizzard in the same way a music clip is monetized on YouTube). They can then possibly file a lawsuit over the lost potential revenue. Since metrics such as downloads are on public display it will be very easy to calculate lost revenue. The actual revenue lost is more than likely minuscule, and not worth suing over, but the possibility is still there.
What ported models from other games are concerned, Hive's ported asset section is just not big enough to be on the radar for those who created them in the first place, but if Hive does get a DMCA complaint on any of them, they will have to take those assets down within a specific time frame.