Yes, mathman has it right. The P5 adults (not sure about the children) were texture compatible with the DAZ people of the time - so Don can use Mike 1/2 textures, and Judy can use Vicki 1/2 textures.

A fascinating insight into the direction in which Poser might have gone, if you think about it. ;-)

James is his own man; and Jessi, her own woman...