I think it would be worth exploring. I don't see where
it is patented, and I would be surprised if it was.
I think, though, you will want to alter R11 and R12 to
200 ohm (or so) potentiometers, as you can't assume
that the MOSFETs Vgs figures will be the same as the
ones used by the designer, the result being a bias
figure which might be catastrophically different.
Start with R11 and 12 at minimum resistance and bias it
up to taste.....