While I'm not sure what videos use to be free, as a member of Chad's Videos, here is what I know:
There are two sets of videos that are available for both Gen Chem and O' Chem. There are the older videos and the new HD videos. I am pretty sure Chad recommends that you use the new ones now. For me, this has been the best $30 I've spent on study material for the DAT by far.
It may be that the older videos use to be free, and since they added the new HD videos they started charging.