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 SVN and try compiling it yourself:
svn co https://freedict.svn.sourceforge.net/svnroot/freedict/trunk/freedict-editor 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
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