Frankly it's disgusting that there are thieves amongst this community. Plain and simple, you are a thief if you are deliberately breaking the licensing arrangements for any mods by using them on multiple forums when you have just paid for one. Please do the right thing and pay for multiple licenses if you are using on more than one site.
Can I suggest that, not only are these thieves given restricted access to other add-ons, but can you also restrict their access to the support forums? I'm always willing to help others but I'd rather not give support to people who are cheating our add-on developers out of their hard-earned money.