You are giving me too much credit Gabreille. I wish that I could help you but I can not. I do not have any Daniel Jacobus Joubert information in my database yet. I specialize in the Joubert branch that moved from the Poitou area in France to Canada in 1669. In Canada alone, there is 3 strong Joubert branch that came from France and from the work that I have done so far, they all have different ancestor.
I suggest that you e-mail Kenneth Joubert. You will find some of his posting in "genforum.genealogy.com". He is from SA and has research that branch of the Joubert. If you go to "ancestry.com" and do a search on Daniel Joubert, you will see many posting from SA. CyndisList.com has over 100 links related to SA. You may also want to do a search in "rootsweb.com".
I hope that this will help you some. You will need to find out where in USA that he died and write that info in your message.