The amount borrowed through credit card is personal in nature hence there is no liability on the legal heirs of the deceased borrower to repay the same.
The credit card loan refers to way back 15 years debit amount, hence it is very badly barred by limitation.
Your friend should not acknowledge the same becasue it is not on his name, if at all the lender bank ant to take any action against the borrower, let them initiate because no action would be maintainable against a dead person.