Ubuntu 25.10’s transition to using Rust Coreutils in place of GNU Coreutils has uncovered a few performance issues so far with the Rust version being slower than the C-based GNU Coreutils. Fortunately there still are a few weeks to go until Ubuntu 25.10 releases as stable and upstream developers are working to address these performance gaps.
Not only that but if you edit the MIT licensed files (Read: They have the MIT notice, which you have to preserve, in them.), they will still be MIT licensed. Only new files and the entire project will become GPL.
I am not a lawer.