This code is from the summer of 2022 when I was integrating for the first time nushell into iox...
The nu_iox folder is the nu-command crate with an additional iox folder which contains all of the nushell iox commands.
The iox_nu folder is the main nushell binary along with a Cargo.toml file which shows
nu-command = { path="../nu_iox", version = "0.66.3" }
the integration of nu_iox into nushell via the nu-command crate.