The first 3 parts of the head video are going to be replaced with DivX versions. Hopefully soon (hint, hint, Kev!
). Parts 4 and 5 are in DivX and should be Mac compatible.
Once you've downloaded a video once, you are not charged for downloading it again, so once the conversion to DivX happens, you can redownload the one(s) you downloaded previously without being charged again for it.