The qBitTorrent project was started in March 2006 to create a lightweight but featureful BitTorrent client that would be multi-platform and very easy to use.
qBittorrent v2 is the closest open source (GNU GPL v2 license) equivalent to µtorrent. qBittorrent is based on Qt4 toolkit and libtorrent-rasterbar.
FEATURE: Show actual protocol for listen success/failure in the log. Needs libtorrent v1.0.0 (Gelmir)
FEATURE: Support per tracker re-announce. Needs libtorrent v1.0.0 (Gelmir)
FEATURE: Support saving in network locations. (Gelmir)
FEATURE: Support Qt5 (mostly Glassez)
FEATURE: Code optimizations resulting in a more CPU efficient and snappier qBittorrent. (sorokin)