VirtualLaunchpad is a patch which looks and behaves like the “empty shell” of a Launchpad. It was originally made so that it would be easy to figure out how to hook the Launchpad into my Max patch when I didn’t have the Launchpad with me.
To use VirtualLaunchpad just open VirtualLaunchpad.maxpat and re-assign the MIDI input and outputs. If your patch can send and receive the correct data when your ports are assigned to the ones VirtualLaunchpad is using, then when you plugin your hardware and re-assign those ports to the “Launchpad” ports, it will just work.
Mira and VirtualLaunchpad
The patch recently became more useful when Mira was released because now you can use an iPad to interact it. Though there is the question of “why would I do that when I can just put my Max patch directly on the iPad via Mira?”. So in reality, while the Mira benefit is neat, since it still doesn’t provide a physical feedback and you can’t take your eyes of it when using it it is not a huge win.