“RustRover is available through a paid commercial license or a free non-commercial license, the latter for individuals using RustRover for non-commercial purposes.”
JetBrains used to give Rust developers IntelliJ Rust, an open-source plugin. Now it sells RustRover, a separate IDE with a paid license for anyone doing real work. The AI features cost extra through yet another subscription. Rust grew a big enough user base and JetBrains moved the tooling behind a meter.