Why is the most permissive license to choose from just CC BY-NC? What if a person licensed it as just CC BY or even CC0?

Also, I notice many tracks are listed as CC BY-NC-ND, but I have a feeling that has a lot to do with the fact that that's the default choice. I dunno, I think remixes can be pretty cool...

And finally, I think it would be neat to be able to filter searches by license.

Thanks!