I think the correct approach is to release an update that adds a link to buy the paid version, and disables the app after a trial period. It should have been d

I think the correct approach is to release an update that adds a link to buy the paid version, and disables the app after a trial period. It should have been done this way to begin with, usually there are two version in market (free and pro or something). Now that he screwed up, users can just refuse to update and keep it forever. Of course, they won't get updates.