From what I see, it's cracked, but as you heard, it's convoluted as shit, making it very slow to replace or extend.
Yeah, the slightly longer version is that Vren (the original author) made it so that there's an image file of every body type in every pose. I
think that things like boob size or visible pregnancy are hot-swappable on the nude "paper doll" image, but don't quote me on that as it's been for-goddamn-ever since I looked.
Then on top of that, each clothing item had to get modeled on each of those poses, on each of those body types, in each "state" it can be in (e.g. shirt on is different from shirt on but tits out). BUT, unlike with the body where you can just have a how-swappable box for different tit or belly sizes, each upper-body thing had to be rendered separately (because the shirt or bra or dress or whatever will potentially look VERY different on a girl with A-cups than if she's rockin' some GGs).
That's a big part of why the last few "official" clothing items that got added were functionally reskins of existing ones - patterned shirts, stuff with words on it, etc. Way easier to add since the files are all right there already & just need tweaked.
I'm not gonna claim to be a programmer by any stretch of the imagination, but I can't honestly think of a better way to have a system where any given NPC (with a default population of like 70 or 80? I think?) can have a functionally unique outfit (accounting for things like color, style, transparency level, etc) that is accurately depicted on-screen. Hell, look at HHS+ - they've got a
kind of similar system, but they stuck to "you get one set of pre-made, not-modifiable outfits that change depending on how lewd everything is (but which are all still pre-made and not truly dynamic) and also everything is on a 2D person who is standing up and facing the camera head-on with MAYBE their arms in a different pose then the identically-outfitted person next to them". Less dynamic system, far more restrictive interaction with NPCs - BUT, if you want to add a new set of outfits, it's
way easier.
So that's the tradeoff I guess. And while yes, obviously you could instead do something in full 3D (like, idk,
name-an-Illusion-game), Vren was one dude making this in Ren'py - not a whole-ass studio with an actual engine and such. ¯\_(ツ)_/¯