It's up to you :) Yes, this layout of miniBB forums could be done as Google mobile friendly. However if we talk about desktop layouts like the current one, obviously I am for the approach when the mobile and desktop are different versions (because when making something for mobile, you actually sacrifice a lot of free desktop space which still could/should be used). It's an utopia to create fully operational forums in the mobile layout. There are too many elements on the screen to fit the mobile device.
Also, the newer release of miniBB which I'm working out these days, will include a different approach to handle mobile and desktop versions at once.