This is were MyBB 1.9 's new responsive theme is being demo -ed . According to the team, it is more or less complete. You can register and see how it works. The responsive part really works, you can see that for various screen sizes. Check the link from mobile too.
MyBB 1.9 release date, price. If these are what you want to know, MyBB 1.9 is free and open source. As for the release date I can only say that somewhere in 2020.