It varies. So, of the ones I've done so far, there is very little impact. He does do a lot of burpees, mostly in the cardio workouts, but also on Strength WOD 4. However, he also has a modifier who, so far at least, has modified the high impact moves to low impact. For instance, in Cardio WOD 2 there was Goblet jump squats. She just did Goblet squats. The Strength WOD 1 I did yesterday was all low impact--and yet it torched me. I would compare impact level of Strength WOD 1 to Afterburn--but harder. Of course it is 1/4 of the length of Afterburn, but I couldn't sustain one of Bob's WODs for an hour! No possible without recovery breaks!
It also looks like Cardio WOD 3 (one of my doubles today) has tuck jumps and jump squats. I will post later today and let you know if he offers modifications. But other than those 2 Cardio WODs, I am not seeing anything higher impact other than the burpees. I watched the breakdown for every WOD before I did any of them and recorded the exercises, so I at least know what to expect before I do them! the Core WODs are all low impact and it looks like of the Strength WODs, they are all low impact except WOD 4 which has the burpees.