By definition, he has been exonerated. The legal definition of exoneration is "The removal of a burden, charge, responsibility, duty, or blame imposed by law". There was an investigation into the company Biden subsequently joined the board of, including an investigation into Biden's role in the company, and found he committed no wrongdoing. There was evidence of corruption within the company, but it occurred 2 years before Biden joined the board.
That being said, it should be considered inappropriate for a family member of a prominent US government official to parlay that family connection into foreign business dealings.
As inappropriate as that is, it's not in the same league as using taxpayer money to extort favors from foreign governments for personal political gain.