Dina Temkin contributes a literal version of Mikhail Lozinskij's version (c.1920?) which is at

Дорогой синьор,

Раз доблесть - это светоч благотворный,

То зять ваш - светлый, а никак не черный.

"Since honor* is a light** of virtue***,

Then your son-in-law is light [as in light-skinned], and by no means black."

* or bravery, heroism, valor, prowess

** or light-source such as a torch

*** or benevolence, wholesomeness

ad hoc version and back-translation by Victor Shapoval (2012)

Коль доблести блеск красоты покорен,

Ваш зять светлее многих, кто не чёрен.

If brightness of beauty obeys the virtue,

Your son-in-law is clearer than most, who isn't black.