@Pirata Nervo :
Because you are a more reasonable guy and are more open minded i will try again to expose my legal point of view on this topic.
Even if GPL is viral, the license cannot affect an add-on when the add-on is not installed on it...
If a software developper create a software add-on in is garage
for himself to use on his own non-GPL created forum, do you believe that a different GPL forum in another country will affect his own right to use the add-on, if it work on it, and that it is giving the right to all users of the other country GPL forum to copy his add-on and distribute it in their country on the sole basis that the add-on is working on their own forum?
Any people with a IQ over 100 should understand that in this specific condition the users not respecting the license of the software developper are commiting a crime against its intellectual property!
Now, we will try to go a step further: If for some reason the software developper decide to sell his add-on with a non-GPL license
without permitting to install it on a GPL application, do this give the right to a user to install it on a GPL application and make it virally a GPL by doing this? Absolutely not, the user would be at fault.
So, if we consider legal issues here it is easily understandable that the viral effect of the GPL application would be applicable
only if the add-on is installed legally on the GPL application.
This would be quite easy to chalenge in court and the common sense and the respect of intellectual property of an author would win.
I have been in the legal system for over 30 years, i really know how it is working and i could easily face a group of 50 young lawyers believing they are all mighty knowing gods! A court is still a court and there are things they cannot consider as legal, period.
P.S. GPL licenses are illegal in certain countries, because of their own legal system, did you knew it?