Kurumi is currenly under experimental phase. Don't use it for daily tasks.
Kurumi ("walnut" in Japanese), is a minimalistic PDF viewer based on Rust, GTK4, and Poppler, inspired by Zathura.
License: MIT or Apache-2.0
Note
Although GTK and Poppler are licensed under GPL or LGPL, the Rust bindings are licensed under MIT. So there is no license compatibility violation.
Kurumi uses MIT-licensed poppler-rs by GNOME.