QBR is different from the passer rating. It does include rushing. It also tries to parse out the quarterback's contribution to the yards. For example, a 10 yard pass followed by a 40 yard run after catch is not worth as much in QBR as a 50 yard pass where the receiver is tackled immediately.
Also, it apparently gives a QB more credit if he scrambles and gains 10 yds after protection breaks down than if he gained 10 yds on a QB draw, where he was likely more OL aided.
Again, I have no idea how they calculate it, but there does seem to be a correlation with QB's and Heisman trophies.