The moons of Gor seem to be another topic over which there has been much debate. Here is what the books say about the Gorean moons.
First of all, of course, there are three moons around Gor. One is larger and the other two smaller. One of the smaller moons is named the Prison Moon and the other two are never mentioned as having names.
"I looked up and saw the three moons of Gor, the large moon and the two small ones, one of the latter called the Prison Moon, for no reason I understood." Assassin of Gor Book 5 Page 170
In the first book, Tarl says all three moons are "small" but this might be in comparison to Earth's moon. They usually seem to be full but do have individual phases and there are lunar eclipses.
Evidently, in their orbits they move across the sky fairly quickly for they are said to be hurtling, rushing, coursing, swift, and having fled across the black sky.
As here on Earth, the moons appear to be larger when close to the horizon and then smaller when overhead since it is said that the moons were down to being looming, large, dominating, seemingly close enough to touch to being high in the sky.
They are described as being white and bright, to being faint, pale white disks.
And finally, the largest of the three is evidently the one used to count lunar months and affect breeding cycles.
I did not include references to 'moonlight' or just the plural form of 'moons' but listed below are every mention of 'three moons' and every time the moons are described.
Lastly, as the culmination of Ar's Planting Feast, and of the greatest importance to the plan of the Council of Ko-ro-ba, a member of the Ubar's family goes to the roof at night, under the three full moons with which the feast is correlated, and casts grain upon the stone and drops of a red, wine-like drink made from the fruit of the Ka-la-na tree. ~~Tarnsman of Gor page 68~~