This package is used to convert mail addressbooks from one format to another. It does this by internally converting them to Eudora format and back out, with some degree of lossiness.
The mechanism to add new addressbook formats to the family is fairly obvious, but an understanding of the Eudora format is a prerequisite, which is quite annoying. Some of the converters are incomplete and data is discarded (e.g. importing LDIF data apparently discards everything except alias, realname and email).
This code is quite crufty. While the author should be greaty commended for delving into all the addressbook formats, the package badly needs a rewrite. I tried to add vCard formats for input/output but have been stymied so far by my lack of familiarity with Eudora and it's address syntax.