The Giver/WMG

There are "Birthmothers," but no "Birthfathers" ...
Because the male Elders father the children. The old-fashioned way. They're the leaders--why should they bother to suppress the "stirrings"? They can probably justify it to themselves because their superior Elder genes should be passed on to future generations. The female Elders, on the other hand, don't want to be waddling around for nine months, so they either take the pills or use birth control.

The Giver is the biological father of all children with pale eyes.
He's a sperm donor, like other men in the Community, and his seed is "sown" at regular intervals over the years so that there's always at least one apt Receiver - not all potential Receivers might start Seeing Beyond, for instance, and one child might die before reaching the age of eleven. That's how they inherited the pale eyes and the capacity for receiving memory. The Giver knows this, and knows this is how it's been done, back and back and back; the children have no idea.

The Giver takes place in the Firefly Universe.
This particular planet was an Alliance experiment in progress - constantly monitored with a drugged populace, and no contact with the outside world, much like Miranda. Only this time, with more careful application of the drugs, and genetic engineering, things go much more smoothly. Being a Reader like River was deliberately tied to having pale eyes, so the Giver and Jonas (and Gabe) are Readers who have taken their telepathy to a highly specialized, but powerful level.
 * But River's eyes are brown. And not a particularly light brown either.
 * Because she existed before the modifications were perfected.

The Giver takes place in the Discworld universe, possibly a secluded corner of the Disc itself.
The Auditors of the Universe demand balance for everything, and The Community exists to balance out Ankh-Morpork, which wallows in human nature. Thus, the Community is everything bustling, colorful, creative, smelly Ankh-Morpork isn't.

The book is an allegory for the Garden of Eden story.
The people live in a Utopian society, with no pain, lust, hunger etc. Yet a supposedly good man kills a baby cheerfully. They key point is that what they lack, and what Jonas tries to give them, is *knowledge of good and evil*. This knowledge would make their society impossible, hence evicting them from the garden. (There is even an apple which plays a role in Jonas acquiring the knowledge which he tries to pass on - implying he is Eve rather than Satan.) I actually have Word of God (via e-mail) on this - she said something like 'an interesting idea, I haven't heard that one before.' But due to Death of the Author, we don't have to care about that.
 * I may be an Atheist, but I think this is the best allegory ever.
 * Maybe that's why.

Birthmothers aren't really necessary.
As stated on the main page, the community's methods of population control are not viable in the long term. So they must be capable of developing new life artificially. They only give birth to some babies the old fashioned way because people still remember how it used to be done, and might ask questions if that changed. It's possible that the only girls who are assigned to be Birthmothers are the ones who might otherwise rebel. If their years of pampering don't keep them quiet, they will be physically unable to cause much trouble during their pregnancies. Then they are reassigned as Laborers, which presumably keeps them isolated from the rest of the Community.

Gabriel has a developmental delay.
It explains why he couldn't learn things as quickly as the other newchildren. However, it makes the community's plans to "release" him for being so delayed all the more tragic.

The World of The Giver Is Our world.
The only difference is the existance of a single "country". To the outside, it's just another third word country. The Elders make sure everyone thinks of it that way.

The population has for the most part lost the ability to see color due to genetic manipulation of the rods and cones in their eyes.
In the eye, the cones allow color to be seen, while rods only show things in black and white. Perhaps the genetic scientists had, over generations, prevented the cones from fully functioning so that seeing color is not an option. In some individuals, as a recessive gene, the cones aren't fully disabled, and they begin to reactivate over time. The receiving of memories just helps it along.