rHuGH is very simply HGH that is synthesized in a lab by using E. coli cells that have been specifically engineered to produce the hormone. It is identical to natural HGH in both structure and effect.
However; before anyone goes out and buys any of the HGH sprays in there local GNC (or wherever) it should be noted that those supplements, while containing HGH have homeopathic (very low) dosages.
It's interesting to note that the link you gave states that rHuGH is a "192" amino acid molecule while every other source I've seen states that HGH is a 191 amino acid molecule. Only 1 amino acid in difference but probably a significant difference.