Peer to Peer (P2P) file sharing is not all illegal and there are several legitimate uses of it. P2P or Torrent clients allow several users and big companies alike to allow users to download legitimate software without straining their servers and relying on technologies which are even used by companies such as Facebook for deploying software.
If you are here to look for LimeWire alternatives, let me point you out to an earlier post where we talked about the best P2P and Torrent software available for free. If you are looking for more LimeWire Alternatives, you can visit the alternative.to site where you will find several more options for LimeWire alternatives.
Do remember that sharing files which you are not authorized to is illegal in several countries, please know your local law before you share music/videos or software using P2P or torrents.