The documentation coming with this application includes the list of features in the introduction.
No release of the FreeDict-Editor has been made yet. You can do an anonymous check out the freedict-editor module from CVS and try compiling it yourself:
cvs -d:pserver:anonymous@freedict.cvs.sourceforge.net:/cvsroot/freedict login
cvs -z3 -d:pserver:anonymous@freedict.cvs.sourceforge.net:/cvsroot/freedict co -P freedict-editor
For the requirements, please also refer to the documentation.
If you use Debian etch or unstable, you can add this to your /etc/apt/sources.list (replace etch by unstable if you use unstable):
deb http://freedict.org/debian-repository etch main
deb-src http://freedict.org/debian-repository etch main