I have a premium WP theme I will be selling. I currently protect it with a serial number generated from the "Serials" plugin. So, when somebody orders it they get a serial number and they have to put it into the theme before it will work. That all works. What would be the best way to offer a developers license, so instead of one serial, they are getting 10 serials with that purchase? Would the "Subusers" plugin work for this, or is that too convoluted? Is there a better option I am missing?