The "runtime" word is very confusing in this case.
It's a web application server written in Rust (Axum/Tokio), that has hooks into Lua bindings (mlua) so that application behaviors can be implemented in Lua.
Looks neat. I built a programmable server for Server-Sent Events using a similar stack (Rust/mlua/axum) [1]. I think the Rust/Lua interop story is pretty good.
It's a web application server written in Rust (Axum/Tokio), that has hooks into Lua bindings (mlua) so that application behaviors can be implemented in Lua.