  We give a new nonstandard proof of the well-known theorem that the generator
$L$ of a quantum dynamical semigroup $\exp(tL)$ on a finite-dimensional quantum
system has a specific form called a Gorini-Kossakowski-Sudarshan-Lindblad
(GKSL) generator (also known as a Lindbladian) and vice versa. The proof starts
from the Kraus representation of the quantum channel $\exp (\delta t L)$ for an
infinitesimal hyperreal number $\delta t>0$ and then estimates the orders of
the traceless components of the Kraus operators. The jump operators naturally
arise as the standard parts of the traceless components of the Kraus operators
divided by $\sqrt{\delta t}$. We also give a nonstandard proof of a related
fact that close completely positive maps have close Kraus operators.
