I looked at it and I really dislike some decisions they made. I had a hard time understanding how to write it and IIRC they don't have GPU integration.

Also I find code like this to be anti-ECS https://docs.rs/orbtk-api/0.3.1-alpha2/src/orbtk_api/macros..... They use macros as a workaround for lack of inheritance in Rust. I would not call that ECS.