This one is going to be interesting from a copyright perspective. KAT is a search engine like Google or Bing (does Yahoo still exist?) and does not supply copyrighted content (at least it appears that way). Maybe they had some other download functionality available as well.

Now they do make millions of dollars from advertising around the search engine so that one could be a problem… although Google does too.

Point being “they don’t deliver copyrighted content” so if you go after KAT, seems you would need to go after Google and other search engines as well.