Membership fee calculates membership fees based on a member's role affiliations.
Membership fee is a plugin for the online membership management system Admidio (https://www.admidio.org) and cannot be used without it.
Online documentation is available here: https://www.admidio.org/dokuwiki/doku.php?id=de:plugins:mitgliedsbeitrag#mitgliedsbeitrag
The change history provides detailed information about the bug fixes and improvements in each version.