This is port of the uc_fee module ( http://drupal.org/project/uc_fee ) with some new features to accommodate how ubercart marketplace deals with sellers, while missing some other features.
Sellers can add as many fees as they would like to their own store.
Administrators can make "Universal" fees that apply to all sellers/stores on the site.
THIS MODULE DOES NOT INCLUDE product fees/classes in this version. The type of fee provided in this module currently only applies to an ENTIRE ORDER as either a FIXED or PERCENTAGE fee.
First download /install the module. Once the module is installed, while still logged in as an admin, goto your account page ( /user/1 ). In there you should see a new section called "Manage added seller fees". This section has two separate functionalities depending on the permissions of the user who is accessing it. One permissions is for "administrator" and one for "sellers".
The two permissions that control the fee form are:
1.)administer own fees
2.)administer all fees
The "adminisister all fees" permission displays a more complex form to fill to add/edit a fee, this is because the administrator can modify any fees on the system set by any of the sellers. In addition to this, a user with "administer all fees" has a SPECIAL option to make a fee "Universal". By making a fee universal, it will apply the fee to all sellers regardless of whether or not that individual seller has any fees on their store or not.
The "administer own fees" permission simply gives the users with that permission ability to manage their own fees that ONLY apply to their store.
Once you have fees setup as an admin, I suggest you log into a seller account and see what that same fee form looks like as a seller as opposed to an admin.