What are some alternatives?
When comparing Shareaza and RetroShare, you can also consider the following products
eMule - eMule is a free peer-to-peer file sharing application for Microsoft Windows.
Soulseek - Soulseek® is a unique ad-free, spyware free, and just plain free file sharing application.
BitTorrent - BitTorrent is a peer-to-peer program developed by Bram Cohen and BitTorrent, Inc.
aMule - aMule - the all-platform P2P client!
qBittorrent - Lightweight and open source torrent client that runs on all major platforms.
Tox - Send messages, files, create groups and make Tox to Tox audio and video calls. Securely.