Any time you see a field like this showing up in Product Maintenance, it is because it is an attribute. If it is not a system installed attribute, it was created when you installed the module.
Removing the module, unless there is a specific uninstall routine, does not remove attributes once created.
!!Using a test install on your DEV server!!, remove the attribute through Attribute Maintenance and then test heavily to make sure it is not referenced in any templates or module code. Typical errors for a missing attribute will throw
Call to member function getXXX() on a non-object in xxxxx.phtml or similar.
If your test system passes with flying colors and doesn't throw any exception errors, congratulations, you should be rid of an unwanted attribute.