Sir John Hawkins, Johnson's executor, certainly thought Barber's legacy was too great to leave to a Black person. As for the "adoption" or otherwise, it's certain that Johnson considered him far more than a servant; more I think a companion (NO sexual overtones); the legacy was less than would have been left to a son, and was placed in trusteeship despite the fact that Barber was almost 40 years old (IIRC). I think this reflected Johnson's fears of his inability to cope with sudden wealth- because he was a servant, not because he was Black.