A magical event
Why can't you just have a plain old-fashioned genetic mutation ? Once you start using magic to solve problems it becomes arbitrary and you loose any constraints, because if magic could solve the problem once, it can solve another problem.
has led to people with similar gene structures to humans coming around, though they can be drastically different in appearance interbreeding is possible. Despite this the magic prevents hybrids it is a simple toss of the coin.
Ah, yes, magic again. See what I mean ? :-)
Reality : an "on/off" breeding decider requires that you pretty much have only one genetic sequence that controls the entire thing, rather than the more likely multiple sequences. Why would a single gene sequence control whether or not you have dense bones or light bones, a wing-like flap, an extra eye lid and any other random bots of anatomy you require.
More likely you'd have people with some, none or all traits.
In this question I beg a couple questions, the social repercussions of Skydancers living amongst humans or near them, natural developments in society to dealing with them in day to day life and if they are even possible or if their biology needs to be changed to ensure they... work.
You actually suggest they don't mix socially normally, so there are no repercussions unless they compete with us.
Mixed breeding would complicate that as a significant minority of humans don't tend to react well to even slight differences between people. So initially a lot of racial tension and possibly violence on a small and large scale. As things develop, probably a tendency for increasing integration as the two sub-species develop a happy middle ground.
Preferred name: skydancers
Probably done already - ya might want to check that.
Physical traits: A race often seen shooting past in the blink of an eye, skydancers are very lightweight people with hollow bones.
Lightweight bones probably isn't a good (or useful) trait for a flying creature whizzing through the air and sometimes whizzing into solid objects. The word "damage" leaps to mind.
Bone is, AFAIK, about 20% of body mass when it's dry. You're not really saving a great deal of mass by concentrating on this issue.
Gliders don't need to be light as such, they need good aerodynamics, some way to control direction of flight, and sufficient lift surface to make the whole thing viable.
If you're planning to develop a gliding race then you really need to learn about gliding - how it works, why it works. The word "thermal" should have a particular meaning to you, for example.
They have flaps of skin underneath their arms that can be pulled taught to act like a wing suit or be folded up under the arms when not in use.
To access these flaps at will they would need to be be unclothed at least in that area. That does suggest a need for either living in the warmth (seasonal migrations ?) or some warm surface layer (fur, leathers ?).
They have 2 sets of eyelids. One transparent and one opaque. This allows them to keep things out of their eyes while gliding.
Another genetic switch !
They are known for their incessant need to climb tall thing and then jump off of them, something of a natural addiction carried by all skydancers by this point.
Sounds a bit robot like. Not the behavior of sentient beings.
More likely they would employ their ability to glide when it's useful for transportation, eat, defense or simply for fun. Even humans like to fly (well, some humans).
They could even use it to make money !
Relationships with humans: often too busy looking for something to jump off of to stop and chat they move in flocks.
Robots again. These are supposed to be human-like. Humans are social creatures. They mix, they form groups and we're even inclined to mix with other species (dogs, cats, horses and some less common associations).
Why would your human-like creatures be any different ?
Scaling tall structures and flying together.
Robots again ? :-)
Are you sure these are supposed to e a branch of the human species ?
It is how they catch food
They can't get jobs ?
They can't find some way to use their skills to generate income ? Just in terms of becoming delivery people in a city they'd clean up - no more bikes ! Police and medical flying units takes on a whole new meaning.
And they have human brains. They can't use they for anything but diving off buildings in search of food ?
And what food ? They're mostly human and they should end up with our very versatile digestive system. There's no reason theses creatures shouldn't be queuing up outside Italian restaurants (assuming the get work) or hanging out in the supermarket or in coffee shops.
and as a result have no need to join society.
Hard to avoid our society - it's getting to be practically everywhere.
And hard to avoid a society they have more in common with genetically than anything else.
They sleep like bats, hanging upside down.
Not a good idea for humans to do a lot, so probably not a good plan for a homo fuga either without drastic rewiring - oh, do I hear the word "magic" again ? :-)
A complete irrelevance and something that, in humans, relates entirely to the local culture and is constantly changing. There's no reason to think that one group of skydancers will share the same cultural norms with another. They're human-like, they're going to have a wide variety of cultural behaviors.
And if they mix with humans at all, there would inevitably be some mixing of cultures - humans do that and so will homo fuga and homo sapien.