its pretty much ok to own the domain.
As far as value... as is usualy for past living president, the domain will probably get traffic and value once he passes away. Kind of morbid really.
The same applies for painters, artists etc...
Even though he didn't have the greatest of presidencies, he is a well respected man and accomplished humanitarian. In this case, I think .us is appropriate. I don't really foresee any problems with owning this domain, but I don't see much value either.
Considering the vast wealth of accomplishments and material on him, I would think development is the way to go here.