It's a Kanban board, another technique for dealing with projects. There are several of these available online (AgileZen, Kanbannery) although I have to admit that Trello is very nice looking. Would be more difficult to use this for an entire GTD system than a list manager but it might be good for a segment of GTD, for example - project plans.

If you try it out as part of your system I would be interested in seeing what you have done with it. I personally will pass on it.