I am my families historian and by all means YES you can make copies of the CD's to share with other family members that is what we make them for. Sure we do a lot of research and yes it takes a long time and sometimes a lot of money but that is our choice and the choice of offering him some money to help him out is a good idea but by no means should he or any family historian ever charge to do the work unless it's for someone else family.
I have spent years collecting information the would have other wise be lost and/or forgotten. The whole point of me collecting this stuff is so I can SHARE it with all my family.
So the answer is YES!!! BY ALL MEANS, PLEASE DO SHARE!!!!