Take a look at these screenshots of the License Manager wordpress plugin.
 
Very easy to install into any WordPress site, with all license management systems running from the WordPress admin area.
 
The 3 config areas that you can see are:

  1. The Products that are being licensed,
  2. The Licenses that are created, both manually or automatically, and
  3. The License Generators ** Exclusive to CopyProtectSoftware
    Gives you ultimate control over how licenses can be automatically generated for your software

Products

Manage-Products

Update-Product

Licenses

Manage-Licenses_640

Update-License

License Generators

Manage-License-Generators_650

Update-License-Generator