Reading some of the posts in this thread, I really do wonder about the sanity of some posters. Most people who release modifications do not do it for money, they do it to share things they have made for themselves with others.
Why would vb.org coders need an incentive ? - easy, because they are not going to shell out $100 and their free time just to convert modifications to XF. Im certainly not, and Im quite sure a lot of others are not either - and no, there is not going to be some magic mass migration by everyone to XF either. I already posted in another thread that they could offer an evaluation/developers licence - i.e. one that allowed you the software for development use, but not to run a publicly accessible forum. I dont expect it will happen, but one can only suggest.