If one planned on selling Vue 6 without e-on's permission (I know you didn't say that was your intention), then the person receiving it would want to be able to upgrade it-- or at least download the latest patches. So, you'd also have to sell him your member account-- thus defeating the purpose of being able to keep Vue 7 as well.

So, my point is without e-on's explicit permission, selling an older copy of Vue seems like a poor idea. Furthermore, if it were possible, then it would be a good idea for everyone to buy an old version of Vue 6 in order to upgrade to Vue 7, then pass Vue 6 on to the next person wishing a copy of Vue 7, and so on, and so on.