1. What would be the tax treatment?
As you have already stated, the benefit he(the debtor) has received, is taxable income in his hands, if the loan had been taken by him for his business purposes.
[The creditor may inform theCommissioner of Income Tax, in writing, with a copy of his letter refusing torepay the loan on the ground that it has become time barred.]
Waiver of loan taken by assessee for business activity assessable as business income : Logitronics P. Ltd. v. CIT (Delhi) 333 ITR 386
Where outstanding liability due to trading transaction becoming subsequently non-payable, s. 41 applicable : Sashak Noble Metals Ltd. v. ITO (Mumbai) 11 ITR(Trib) 335
2. If now he says to the tax department that it is a loan, then would that mean it is no longer time barred and is now recoverable?
If it is a loan time barred and not intended to be repaid, it is taxable income in his hands, if he had taken the loan for his business purposes.