Ultracopier

For my is the best copier at this time, evolve very ofter, open source, ...

Multi-plateform (linux, mac and windows)
Written in C++ for all peaple can develop
Lot of version (normal, 64Bits, portable, debug)
Written in Qt to take advantage of this lib (translation, themes, css, plugin, ...)
Try standardized a maximum of things and to share up to code, and to a maximum of lib internally and with other Copiers
Increased vigilance for the safety of transferring data
Very good roadmap and technical document or simplified, good community and very responsive developer (I have tools for high performance instant notification)
Nice site tailor-made and a platform to create a great community
Updated regularly, svn version available for the latest version not yet released