I needed a similar script a few months ago and I did some research on available pinterest-like layouts. As you, I found most too bloated so ended up writing my own. I also noticed that a lot scripts read-size/write-css alternately, instead of calculating all at once and then applying all at once. Your looks the closest to the perfect one.

But I see some flaws in statements that you mention on the plugin homepage:

Are built on dependencies, like jQuery

That's not true. Even official masonry script by David Desandro has vanilla js version. Also there are https://github.com/henriquea/minigrid and https://github.com/attila/savvior and someone already mentioned Salvatore. And even Woomark has version without dependencies https://github.com/germanysbestkeptsecret/Wookmark-jQuery

Mandate HTML markup, or require a CSS stylesheet

That's also not true, most allow to use any markup.

Position elements with transforms, making animation difficult

It's actually the opposite. It's much cheaper for browsers to animate elements that are positioned with transforms.