According to the announcement,
Registration is required, but free. Once you have registered, you can search through the idioms, add new idioms, add translations and definitions, and generally contribute to the site.IDIOMIZER is a translation
reference for idiomatic exchange across languages, absolutely vital
because different cultures use different phrases to impart the same
meaning. One of its many powerful features is the ability to view
multiple languages simultaneously.IDIOMIZER seeks the input of translators, linguists
and language lovers worldwide in making the site a useful and enjoyable
tool and we encourage you to register and add to our idioms.
Perhaps this is not “absolutely vital”, but it should prove a useful addition to many a translator's toolbox.